(The scene is Happy Bear Ice Cream. A large truck is leaving. Cut to another truck being loaded.)
Truck driver: (on the phone) Yeah, it's a truckload of ice cream. What's the worst that could happen?

(Cut to a cake factory. A truck is parked outside.)
Truck driver: (on the phone) Yeah, cake's all loaded up. We'll be there. What's the worst that could happen?

(Cut to an airport. Boxes of TNT are being loaded onto a plane.)
Pilot: (on the phone) Yeah, we're loading the dynamite onto the plane now. What's the worst that could happen?

(Pan over to the school. Within, Milo attempts to use a water fountain that knocks him over with a jet of water. Melissa and Zack look on.)
Milo: No problem. I've got a dry change of clothes in my locker. Yelp! (Milo slips in the water) See you in a bit. (Milo walks off)
Melissa: So, tomorrow is Milo's birthday.
Zack: Is he having a party?
Melissa: Probably not. The last time he did, it did not end well.

(A flashback shows a fireman chasing a horse at Milo's house with all the emergency services parked outside. Two helicopters hover overhead.)
Fireman: (as the horse runs and whinnies) Whoa there! Whoa there! Whoa! Whoa whoa whoa whoa whoa whoa whoa whoa!
(The house explodes with confetti as paramedics load a moaning clown onto an ambulance. The flashback ends.)

Melissa: After that they only invited immediate family and... me.
Zack: Well, that's sad. Doesn't he miss having a big birthday party?
(Melissa's phone rings. She answers, opening a video chat.)
Melissa: Hi, Mrs. Murphy.
Brigette: Hi, honey. Uh, do you think we should invite Zack tomorrow? And if so, does he have proper coverage?
Melissa: He's right here. (tips the phone to show Zack)
Zack: Hi, Milo's mom! I overheard, and I'm fully insured. Um, just a thought, but is it okay if we invite some kids from school? It could be a surprise.
Brigette: Hmm. Let's check with Martin. He's still at work. (Martin is added to the chat) Hi, dear! Melissa and Zack were thinking of a surprise party for Milo tomorrow. How's our liability coverage?
Martin: Oh, better idea; not in our home. We could do it at the Play Park.
Zack: Yeah, the go cart track!
Martin: It'll be perfect. (things drop onto him from above) They already have all the party supplies, fire extinguishers, helmets, first aid kits —
Brigette: Plus, they're fully insured.
Melissa: So, we can invite people?
Brigette: Sure.
Zack: Great! Surprise party!
Martin: We'll have to keep him busy all afternoon so he doesn't suspect.
Melissa: We'll handle that. See you tomorrow. (The water fountain partially dislodges from the wall, spraying water.) That's weird, nobody pressed the button. (The water fountain falls off the wall, and a water jet knocks over a student. Milo arrives shortly after in his usual clothes) Oh. Hey, Milo.
Milo: Hey, guys. (Milo stops the water pipe)
Melissa: Did you change?
Milo: Yeah, this one's all dry. I have, like, thirty of these.

(Melissa and Zack hand out invitations to other students outside the front door of the school.)
Zack: (whispering) Surprise party for Milo.

(Melissa is approaching two girls on bleachers.)
Melissa: (whispering) Surprise party for Milo.

(Zack is approaching a basketball player.)
Zack: (whispering) Surprise party for Milo.

(Zack and Melissa are in the hallway.)
Zack: (whispering) Surprise party for Milo.
Melissa: (whispering) Surprise party for Milo.

(Zack and Joni are scuba-diving.)
Joni: Won't it be dangerous?
Zack: You're a hundred feet underwater right now, swimming with eels.
Joni: What's your point?

(Cut to a house overburdened with wind-chimes.)
Melissa: So Mort, you coming to Milo's party?
Mort: As long as your dad's there. He's a paramedic, right?
Melissa: Right. (They shake hands)

(Cut to a bungee-jumping platform on a high bridge. Zack, Chad, some other students, and an instructor are there.)
Zack: Surprise party for Milo?
Chad: I don't know. My risk tolerance only goes so high. Waaaaaahh! (jumps off)
Zack: We'll all be wearing helmets. It'll be fun.
Casey: Ok, we're in. Waaaaahh! (The other students on the platform jump off)
Instructor: I like parties.
(Zack looks away awkwardly)

(Cut back to a room within the school. Amanda is organizing the yearbook. A student is presenting her with a sample page.)
Amanda: The border on this photo is a millimetre thicker on the left than on the right. You have a split infinitive in the caption. (The other student goes away; she turns back to Melissa) I don't know, Melissa. Things get sort of messy around Milo. You know how I like order.
Melissa: (looking in a book) I understand, Amanda. I'm trying to figure out the streamer situation. But I guess it doesn't matter if there's really a cohesive colour scheme, and the balloons I'm ordering are all different sizes and shapes, (Amanda starts to panic) but I can't imagine that it's going to be a problem really, you know —
Amanda: Alright, I'll organize it! "Cohesive colour scheme doesn't matter." (beat) Don't think I don't know what you just did.

(Cut to Milo working on the roof of his house. Melissa approaches with her arm in a sling.)
Melissa: Yo Milo, what up?
Milo: Hey, Melissa. Just installed the new asteroid early warning system. (takes off his goggles) Oh, what's with the arm?
Melissa: Sprained it. (Milo slides down the ladder) Problem is my dad has an important package to be picked up at the mall. I can't do it with this arm. (Puts on her doe eyes and bats them) I know it's your birthday and all, but any chance you could pick it up and drop it off at this address? (hands Milo a slip)
Milo: (taking it) Sure. Be happy to help. (They enter the house) Think of all the times you helped me when I had a sprained arm. Or leg. (a lamp on the wall falls out) Or... spleen. (They exit through the front door) Or tongue, or finger...
Melissa: Twice.
Milo: (goes to his bike) Or clavicle, or rib-cage, or metatarsal...
(Milo mounts his bike.)
Melissa: Thanks, Milo.
Milo: No problem.
(Milo rides off, and Zack emerges from the bushes. Melissa removes her splint.)
Zack: Nice acting job.
Melissa: I had to bust out the doe eyes. (Does her doe eyes) Use only in case of emergency.
Zack: What if he shows up too early for the party?
Melissa: I’m way ahead of ya. Remember Elliot, the crossing guard? (rings her phone)

(Cut to a crosswalk, where Elliot is acting as a crossing-guard.)
Elliot: Be sure to watch your step. And I mean that in two ways. I mean watch your step, and, watch your step. (His phone rings) Elliot here.
Melissa: Is this Elliot, who monitors local safety violations?
Elliot: Well, "safety first" is certainly one of my six safety-related mottoes.
Melissa: I’d like to report a violation. I just saw Milo Murphy’s bike, and the back wheel is a definite safety hazard. It might fly off any second.
Elliot: You had me at Milo Murphy’s bike. (hangs up) You’re on my radar, Milo Murphy. (looks at his radar, on which is one dot which splits into dozens of little dots) Oh wait, no. That’s a flock of birds. Wait, wait. There! Now you’re on my radar, Milo Murphy.
(Cut to Milo riding, dodging obstacles that fly towards him. Elliot stops him.)
Elliot: Stop! (turns his sign around) Milo.
Milo: Elliot. You might wanna duck.
Elliot: (Elliot ducks as he looks out for dangers) huh! Mm. Mm. Mm.
Milo: No. I, I mean you might want this duck. (Milo produces a duck from his backpack) I found him wondering in traffic earlier and I… you know… I figured, with you being the crossing guard —
Elliot: Safety czar!
Milo: — safety czar, you might be able to get him somewhere safe.
Elliot: (pauses and looks around) Well, there is a little pond right over there. (Elliot grabs the duck) Don’t move! Do not go anywhere!
(Elliot slowly backs away and carefully puts the duck down while looking at Milo, giving him the "I'm watching you" gesture. The duck quacks at him aggressively and then proceeds to chase him around. Elliot screams and yelps as it does. After a few seconds of this, he falls into the pond, and the duck pursues. He climbs out of the pond with the duck jumping on him. He gets the duck off him and scrambles away. The duck peacefully returns to the water, and Elliot storms back over to Milo.)
Elliot: I have reason to believe your vehicle might be unsafe. I’m going to have to inspect it.
Milo: Okay, but you might wanna duck first.
Elliot: Don’t be ridiculous. You couldn’t possibly have another duck back — uh! (is knocked over by a tire being carried by a helicopter)
Milo: No I meant because of the tire.
Elliot: Just for that, Murphy, you’re getting the full inspection. (produces a clipboard)
Milo: Well, I did my own inspection this morning, but I guess you can never be too safe.
Elliot: Oh yes you can… not be too safe. (starts inspecting)
Milo: Do I have to remove my shoes?

(Cut to the Play Park Go-Kart Fun Track.)
Martin: This is perfect. The track makes everyone wear helmets and fireproof jumpsuits.
Brigette: Oh, great. For once we won’t look out of place. (puts on a helmet)
(Some students arrive with more party supplies.)
Martin: Ah, (puts on a helmet) thanks for helping us set up, guys. Time for our checklist. Fire-retardant netting? Check. Radiation screens? Check. Glow-in-the-dark t-shirts in case of power outage? Check. Let’s get to work.

(Cut back to Elliot and Milo.)
Elliot: Alright, Mr. Murphy, you passed. Barely.
Milo: Hey, cool. See ya. (rides off)
Elliot: Straighten that helmet! I’ve got my super safety senses trained on you from now on! And I mean that two ways! Actually, it’s just one. (The duck attacks him again; he screams)

(Cut back to the go-kart track.)
Amanda: Your party planner has arrived with the bubble machine. Chaos is over. Order begins. You, cards on every table, colour-coded by age, gender and cake preference. You with the funny hair, these banners should be all five feet from the ground. You, nail-biter, make sure all the utensils are parallel to each other. Step to it, people!
Martin: (dragging in a pile of mattresses) And we brought matresses to hide under in case of falling debris.
Brigette: Plus, we can wrap ourselves in them for duck attacks.

(Cut to the mall. Milo arrives and is handed a package at a window.)
Milo: Wow, that was convenient. All malls should have drive-through windows.
(Milo continues up a hill, dodging bins, ball bearings and slinkies.)
Milo: Hmm. Kind of a light day.

(Cut back to the go-kart track. Amanda holds a remote-control.)
Amanda: Okay, everyone. Clear the perimeter. And Murphy’s Law countermeasures engaged.
(She pushes the button. Sensors deploy around the perimeter, and an alarm sounds.)
Sara: He’s a block away, t-minus twenty seconds. Roll in the decoy!
(Two students place a fake sign over Play Park’s actual sign and then dive into a nearby bush.)
Kris: I’m planning on staying in this bush the whole party. Amanda scares me.
(Milo rides up.)
Milo: (reading a slip of paper) "Industrial Industries, serving the industrial needs of industry for over fifty years." This looks like the place.
(Milo enters and finds all his friends waiting for him.)
Everyone: Happy Birthday, Milo! (They cheer; noise-makers sound)
Natalie: I like cheering!
Milo: Wow, you guys! A real birthday party?
Melissa: Got ya. (fist-bumps Milo)
Milo: You used the doe eyes.
Zack: And they’ve got go-karts! They're karts that go!
(Everyone races to the go-kart track. "I Gotta Go" begins.)
Milo: This is great, you guys. Let’s go!
(They race in the go-karts.)

Singers: Well I’ve got no time for trivial things
Gotta get up and get out into the world
Find a spot in the manner of kings
Gonna blow into the city in a whirl

I gotta go

(Alex spins out on some oil that comes out of Zack's go cart and lands on a pile of sandbags to the side of the track.)
Alex: Okay!

Singers: Oh, I’m Mister Go
They call me Mister Go
(Instrumental bridge.)

(A loose screw from Milo’s go-kart hits the helmet of Mort and distracts him long enough for him to lose control of his go-kart. A wheel from his go cart breaks off and flies into the protective netting. Amanda, who is watching, gives the thumbs-up. It is catapulted out of the Play Park. The wheel then knocks over Elliot. He screams. Meanwhile, the party-goers continue racing.)

Oh, but you know I gotta go
Gotta get gone getty gone gone

(A billboard becomes loose and falls on the track, being propped up by the barrier. Milo, Zack and Melissa fly up it and out of the go cart track, landing on a table. This launches Amanda’s bubble machine and some balloons into the air. "I Gotta Go" ends.)
Milo: (as he, Melissa, and Zack get out of their karts) Did you see that? That was awesome!
Melissa: Uh oh. I think that was Amanda’s bubble machine.
Zack: And we have all of our limbs! Well, except for One-Arm Willie.
One-Arm Willie: It’s a nickname. I have both my arms. I am missing one leg though.

(Cut to the "Happy Bear Ice Cream" truck on the road, then to the "Cake" truck, then to the plane hauling dynamite. The bubble machine lands on the road.)

(Cut back to the party. The students all chant for cake as they hold up plastic screens between them and Milo.)
Students: Cake! Cake! Cake! Cake!
Zack: Milo and candles. Can’t be too careful.
Brigette: (to Martin) I’m afraid we have a problem dear. Diogee got into the cake and ice cream.
(A chubby Diogee among the remains of the cake and ice cream looks at them, full of guilt)
Brigette: Sorry, Milo. The cake got ruined.
Milo: Though cake and ice cream would have been nice, I already got my wish. (cut to the balloons ascending toward the plane) I had a birthday party, and nothing went horribly wrong.

Pilot: Ooh, balloons!
(The pilot accidentally leans on a lever opening the cargo bay door, and all the dynamite falls out of the plane.)

Driver of the ice cream truck: (as he drives through the bubbles) Huh? Whoa. Yah!
(The truck swerves off the road and launches its cargo high into the air.)

Truck driver #2: Oh no, duck! Yea, ugh! (The cake delivery truck swerves to avoid a family of ducks crossing the road and stops on an unfinished overpass, launching cakes into the air.)

(The dynamite, ice cream and cake all collide and create a large explosion right above Play Park. The students all look up in wonder.)
Milo: This is the best birthday ever!
(Everyone is quickly covered in falling ice cream and cake.)
Milo: Ice cream and cake? Correction! This is better than the best birthday ever!
(Everyone cheers, but they are soon interrupted. They run away screaming as the duck family attacks.)
Martin: Quick, everyone wrap yourselves in mattresses!

(The end.)