Kevin made his first and only appearance in the episode Shame. It started with Malcolm playing baseball with Stevie. Malcolm threw the ball to far and when he went to get it, Kevin picked it up before he did. Kevin kept taunting Malcolm with the ball and doing things such as repeating everything he said and calling him "stinky".
Later, Kevin cut in front of Malcolm in the lunch line, and took the last of the frozen pizza. Kevin then came to Malcolm's lunch table and mocked him some more. Chewing pizza in his face and continuing to repeat him. Malcolm tried ignoring it, but Kevin spitting pizza sauce on his face was the final straw. Malcolm retaliated by beating Kevin up, making all the kids around him and even the lunch lady chant "Fight! Fight! Fight!" for him.
In the next scene, Kevin was crying in the nurse's office and Malcolm was in huge trouble because Kevin turned out to be only 7 years old and in 2nd grade. It was also revealed that it was Kevin's birthday that day and Malcolm had beaten him up. Malcolm was completely guilt-tripped by the school staff, being called a "thug" and many other things. Malcolm had to deal with this for the entire episode.
Later in the episode, his father came up to him and confronted Hal because of his son beating his underage son. He pushed Hal and repeated him, doing all the same things that Kevin did to Malcolm. Hal then beat him up, only to realize that he was only 15.
- It must be a genetic trait in his family for people to be much bigger than the normal size for their age because he and his brother are both extremely big and tall for being 7 and 15.