Mikey joins Cobra Kai following Miguel's victory against Kyler in the lunchroom fight. He is seen in the junkyard training montage in Molting. When Sensei Johnny Lawrence gives them some jerky to eat during practice and calls two dogs to attack them, Mikey runs, jumping and sliding over a car.
He forms a good relationship with Hawk and helps him carry out various tasks against Miyagi-do. Mikey is present when Hawk confronts Demetri in a comic book store along with Chris, Mitch and Doug. Hawk demands Demetri to take down his Yelp review about Cobra Kai, but Demetri refuses, resulting in the gang attacking him after Demetri pushes him and Doug aside in an effort to escape. Robby and Samantha manage to intervene, resulting in a fight breaking out. Hawk looks at Mikey and they smile before they attack. Mikey, along with the rest of Hawk's gang, ends up getting beaten in a fight.
Encouraged by Kreese, Mikey helps Hawk to vandalize Miyagi-Do Karate dojo and steal the Medal of Honor which belonged to Mr. Miyagi. During Cobra Kai training in the woods, Mikey stumbles upon Tory and Miguel. Mikey gets beaten by Miguel and Tory working together, with the latter taking his headband.
On the first day at school, Mikey participates in the school brawl. He and Doug can be seen attacking Robby on the stairs together, however Robby ends up breaking free from Doug's grip and kicks both him and Mikey down the stairs.
Mikey remains loyal to Cobra Kai after Kreese takes over the dojo from Johnny. He can be seen with Hawk, Mitch and Doug having fun and causing havoc in the local arcades. The group ends up breaking into laser tag arena to drink beer. When the lights in the laser tag arena suddenly go out, Mikey says "What the hell?" before they get attacked by Miyagi-do students. During the fight, Mikey manages to beat up a Miyagi-do student by kneeing the student's face, before getting punched in the face by Demetri. Initially, the Miyagi Do's have the upper hand, but when Tory arrives with Big Red and another student, the Cobra Kai's gain the upper hand, and Mikey assists Doug and Mitch in beating up Chris. When Hawk has Demetri's arm on hold, Mikey along with the others encourage Hawk to beak it. After Hawk breaks his arm, Mikey and the others cheer.
Later on, Mikey is amongst the Cobra Kai students to attack Miyagi-do and Eagle Fang students who are meeting up in LaRusso's house. He at first, fights Miguel, who throws Mikey down onto the living room table head-first, before Kyler intervenes. He then gets in a fight against Mitch, who ends up grabbing and throwing him into a corner. When Mitch goes and tries to help Demetri, Mikey intervenes and resumes fighting Mitch. When Sam runs away from Tory, Mikey is seeing being knocked down by Mitch and then repeatedly punched by the latter. Later, however, Mikey can be seen being hit by a Miyagi Do student, and is then seen attacking Demetri and Hawk, with the latter having turned against Cobra Kai mid-fight. Mikey is kicked by Demetri and then thrown to the wall by Hawk. He is last seen supposedly spinning during the fight. Ultimately, Mikey and the Cobra Kai's lose.
Mikey is not present when Miyagi-do and Eagle Fang join their forces in the following morning. It can be assumed that Mikey decided to stay loyal to Cobra Kai even after Hawk left the dojo.