Continuity mistake: Kel comes into Rigby's and sits on the counter and takes of one of his trainers, after he has been handing out fliers. He puts it on the counter so the sole of it faces the camera all the time, yet during shots it suddenly changes so that the top of the trainer faces the camera.
Audio problem: The sound of the aspirin hitting Chris is just a fraction before it hits him. (00:02:35)
Continuity mistake: Mo Sweater Blues: For the amount of water Kel splashes on Kenan the wet patch is way to big.
Diamonds Are For Roger - S1-E7
Audio problem: When Chris is hit by the old lady the sound is before the actions.
The Cold War - S1-E8
Continuity mistake: The clock in Rigby's is changing time throughout. (00:04:00)
The Cold War - S1-E8
Factual error: The pilot that jumped at the end isn't descending fast enough to be real.
The Cold War - S1-E8
Continuity mistake: Kel drinks a fair bit of Kenan's "medicine" but in the next shot the amount of "medicine" is greater than before.
The Cold War - S1-E8
Revealing mistake: Cold War: The drill hole Kenan makes at the start is larger than the drill bit.
Revealing mistake: The orange soda cans are supposed to be full but when they fall they are obviously empty.
Continuity mistake: Just before and when the president it in Rigby's The clock keeps changing time.
Continuity mistake: When the President is in the shop and the tower of Orange Soda is about to collapse, watch Kenan. He puts his arm through the display to make it collapse.
Continuity mistake: In the episode when the president comes into Rigby's, near the start Kenan fixes the slush-o machine, but it doesn't work, and slush-o sprays all over Chris. Afterwards, one of the slush cups on the counter falls over. After that, the cup keeps on vanishing then reappearing.
Revealing mistake: When the tower of Orange Soda collapses you can see it falls in segments of cans.
Continuity mistake: When the President is being crushed in the Oval Office, Kel opens the sliding door. The door stays open but when left alone Kenan and Kel go to look at it and it is now closed.
Merry Christmas, Kenan - S1-E11
Continuity mistake: When Kel knocks the Christmas tree over the star lands by Roger's feet but appears on Roger's head as he stands up.
Continuity mistake: There is a 5 minute scene in Rigby's at the end but the clock doesn't move at all.
Answer: He's simply enjoying doing it himself. Especially since he likely believes he can do it better than she can.