Zack is the new kid in town and the voice of reason when things get out of hand. While the rest of the town is used to Milo, Zack is trying to enjoy the adventure of being Milo's best friend without getting destroyed. He wants to follow Milo because he wants a change from common life. In fact, he accepts going to school with Milo because his adventures are unique ("Going the Extra Milo").
He also wants to be safe enough though. In the episode Sunny Side Up, he has no problems on doing a science project with Milo, even knowing that it's extremely hard, but when they made it he didn't let Milo get near to make the project safe.
Maybe because he's new, he seems to not be fully aware of what Murphy's law can cause. He often says that things couldn't go worse, or he thinks that is some case, nothing wrong can happen. Zack is also fairly self-conscious about previously being part of The Lumberzacks, at times trying to conceal the fact from his friends while at others actually hoping to be recognized for the role.
Zack has dark eyes, brown skin, and thick, bushy black hair.
He wears a deep-yellow short-sleeved shirt over a white long-sleeved shirt, revealing only the collar and the sleeves of the latter, alongside a pair of light colored blue jeans with pockets and gray cuffs. His sneakers are a darker blue and white with white laces.
He is slightly taller than both Milo and Melissa and tends to stand with a bit of a slouch, giving off a 'chill' appearance. Likewise, he often sports a cocky, relaxed expression to the same effect.
He was happy to visit his mom on career day and seemed satisfied when the other students noted how cool her job was. Eileen went with him when the school had a parent-teacher night, and the two of them exchanged friendly banter before the meeting ("Worked Day", " Backward to School Night").
Zack expressed nervousness to his father when they went on a fishing trip with Milo and Martin. While Marcus did not initially believe his son over the existence of Murphy's Law, the two of them ended up working together to get the boat to shore ("Time Out").
His father loves to scare him constantly- and would do so every Halloween, coming up with creative new ways to scare him every year. Zack absolutely loved this and claims it was awesome. His father manages to do it again this year despite Zack's belief that Halloween no longer scares him ("Milo Murphy's Halloween Scream-a-Torium!").
Main Article: Zack and Milo's Relationship
Main Article: Zack and Melissa's Relationship
He became good friends with Melissa through their mutual friendship with Milo. He gets along with her well, as the two of them are more level-headed when it comes to Murphy's Law. They often cooperate with each other to finish a goal, as seen when they both work hard to protect their project from potential disasters in Sunny side Up. Melissa tells Zack to loosen up while Zack tends to worry about Melissa's absent-mindedness.
Before Zack moved to Danville, he and his former friends had formed a lumberjack-themed boy band. The five of them enjoyed their fame together until he ended up moving away, although the other members didn't seem too concerned about this. When he did see them again, the band's new leader, Max, provoked a rivalry between the now-renamed Lumbermaxes and Zack's new band, Just Getting Started. After the performance, they tried in vain to get Zack to rejoin ("Battle of the Bands").
Back when they were a band, they hung out together constantly, although they didn't seem to have the closest friendship. When a girl clearly cut in front of Max in a lineup, Zack went out of his way to claim that she wasn't in the wrong, starting a small argument with his bandmate over it. When he finally did leave the band, they barely looked up from their entertainment to say goodbye.
Max, as the voice of the group, doesn't seem to respect Zack much and tends to ignore his words in favor of hearing what he wants to hear, much to Zack's annoyance. He makes immature sounding assumptions that Zack is just using reverse psychology and secret messages to convey his actual thoughts.
Zack is on friendly terms with Mort. They are both players in the Jefferson County Middle School football team, and the two of them are a part of the band Just Getting Started. When Mort, like the others, was stressed out about their first live performance as a band, Zack reassured him it would be fine, managing to calm him down temporarily. And when Mort makes a bizarre comparison between Zack's past and a dance movie cliche, the latter excitedly agrees.
Zack is on friendly terms with Amanda and has teased Milo over his interest in her. Like others, he finds her obsession with order unusual and recommended she switch to tangerine oranges to save time after finding out she had her entire day scheduled.
Zack often seems amused by Chad's unusual antics, standing idly by while Melissa argues with him. When Chad made the suggestion that the punch was blood, Zack briefly pretended it was true to show how ridiculous that was. In spite of this, he was quick to go along with Chad's 'Vampire-hunter' theory and went out of his way to help him defend Mr. Drako ("School Dance").
Zack, being new to the area, is not as familiar with Milo's parents as Melissa is. When Brigette calls Melissa to ask her if they should invite Zack to the party, he informs her that he is fully insured, and even asks if they can make the party bigger.
He tends to be a little nervous around Martin, knowing that the effects of Murphy's Law are multiplied when there is more than one Murphy in the area. He expressed this when he brings his own father on a fishing trip with Martin and Milo, and again when he voices his concerns about skiing with two Murphys. In spite of the extra danger, he enjoys hanging out with Milo's dad.
Zack is on good terms with Milo's sister and enjoys hanging out with her. She spends quite a bit of time with the group, often ending up on adventures with them when things go out of hand. Sara, like Milo, was thrilled to catch him and Melissa up on Doctor Zone, although the latter two ended up more tired and confused about the show than excited. Afterward, while he seems to enjoy the show himself, he tends to find Sara's obsession with it odd.
In We're Going to the Zoo, he hung out with Milo and Sara as they prepared some of Milo's clothing for donation. He claimed he didn't believe Sara when she repeated a conversation she'd had with her mother.
While Zack doesn't know them very well, he is on friendly terms with Cavendish and Dakota. Initially, he assumed, thanks to Chad, that the two of them were vampire hunters, and this led to his confronting them at a school dance. This impression didn't last long, and eventually, they were formally introduced to him by Milo as time travelers.
Zack is often mildly annoyed with Elliot for causing them extra trouble, and treats his antics with skepticism, calling him out whenever he tries to exaggerate his job. In spite of this, he tends to be friendly with the crossing guard.
Zack had a brief crush on the danger-seeking girl, and he forced aside his typical cautious attitude to impress her. He was attracted to her for less than a day before he realized how dangerous she was ("The Wilder West").
|The image gallery for Zack Underwood may be viewed here.|
- In The Undergrounders, he appears to be claustrophobic, which is a fear of closed places; however, he says he's just 'claustro-avoidant'.
- So far, Zack didn't appear once in The Little Engine That Couldn't.
- He states he has a fear of fish.
- Though he has a least attempted to conquer his fear of fish that aren't in a body of water, he goes fishing in Time Out.
- His football jersey number is 19.
- He shares the same last name as Weevil Underwood from Yu-Gi-Oh!.
- Like Ferb, Zack has separate voice actors for speaking and singing.
- Zack being the voice of reason yet a best friend to the main character who is positive is similar to Gerald Johanssen from Hey Arnold! Dan Povenmire worked on Hey Arnold! before working on Milo Murphy's Law.
- In Fungus Among Us, he mentioned that he has at least two younger brothers who he claims can eat with their feet.
- In Love Toboggan, it was shown he knows how to snowboard.
|Milo Murphy's Law characters|