Continuity mistake: In the episode when there is a rat in the store, there is a scene where Kenan and Kel are discussing the rat. There is a lady in the background holding a green shopping basket. Then in a following shot the same lady is now suddenly holding a red basket. Cut to the shot where she runs out of the store screaming, and suddenly her basket is green again.
Visible crew/equipment: When Kenan and Kel are at the White House, after Kenan saved the President's life, and was therefore allowed to visit him - Kenan and Kel open the President's secret hideout, by pulling a book on the bookshelf. Inside the hideout, there is a clear tape-mark strip on the floor. In following shots when the President walks inside, the tapemark strip has now vanished.
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.
Continuity mistake: When Keenan is yelling at the kids playing with the water guns, there is a clip board on the counter that disappears.
The Lottery - S2-E3
Revealing mistake: When Kenan hits Chris in the mouth with the apple, you can tell it was placed in his mouth because he managed to bite the apple, and take a chunk of it out. Normally an apple like that would smash your teeth.
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.
Revealing mistake: Kel is in the Orange Rain and if you look at the road you can see it is just paper by the way it warps. (00:09:50)
Continuity mistake: In the episode when the president comes into Rigby's, near the start Kenan supposedly fixed the slush-o machine, yet it isn't fixed properly and slush-o sprays out and completely covers Chris. As the scene continues, the wet patches on Chris's apron completely change. At one point there are only a few patches dotted on the apron, then suddenly the apron is completely soaked again.
Get The Kel Outta Here - S2-E8
Revealing mistake: Kel walks away the wrong way when told he is not allowed in the house ever again. (00:07:50)
Visible crew/equipment: When Roger is leaving you can see outside the door that the background is a painting.
Continuity mistake: When Kenan and Kel are in the kitchen trying to make the birthday cake, there is a blackboard behind them. The writing on the board disappears and then appears again during the scene.
Continuity mistake: Get the Kel Outa Here: At the start of a 5 minute scene, the clock in Rigby's says 4:30 approx. At the end of the scene, the clock says 4:40. (00:13:00)
Revealing mistake: Cold War: Kel misses hitting Roger when trying to wake him up.
The Raffle - S3-E3
Continuity mistake: Chris comes into the shop and does not lock the door but has to unlock it for the customers to come in. (00:11:00)
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)
Who Loves Orange Soda? - S2-E4
Continuity mistake: When Kenan and Kel are making the bet, the clock on the wall changes time. (00:08:00)
Answer: He's simply enjoying doing it himself. Especially since he likely believes he can do it better than she can.