Visible crew/equipment: When Kel gets up to get more water you can see one of the cameras.
The Cold War - S1-E8
Factual error: The pilot that jumped at the end isn't descending fast enough to be real.
Revealing mistake: The orange soda cans are supposed to be full but when they fall they are obviously empty.
Revealing mistake: The parrot is a very obvious stuffed toy.
Continuity mistake: When Kenan and Kel are in Kenan's room there are 2 socks hanging out of the dresser the one on the left keeps changing positions.
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.
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.
Continuity mistake: Just before and when the president it in Rigby's The clock keeps changing time.
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.
Doing Things The Hemingway - S1-E3
Continuity mistake: Kel is attempting a life goal and attempts to put 50 grapes in his mouth. When he spits them out there is about 10, nowhere near what Kel then claims is 33 grapes.
Visible crew/equipment: When Roger is leaving you can see outside the door that the background is a painting.
Doing Things The Hemingway - S1-E3
Revealing mistake: Kel takes the VCR player without unplugging it but Roger was watching a video seconds before.
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.
The Cold War - S1-E8
Continuity mistake: The clock in Rigby's is changing time throughout. (00:04:00)
Doing Things The Hemingway - S1-E3
Revealing mistake: The clouds are very obviously a set-drop when on the top of the CS tower.
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.
Audio problem: The sound of the aspirin hitting Chris is just a fraction before it hits him. (00:02:35)
Answer: He's simply enjoying doing it himself. Especially since he likely believes he can do it better than she can.