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.
Visible crew/equipment: When Kel gets up to get more water you can see one of the cameras.
Visible crew/equipment: When Roger is leaving you can see outside the door that the background is a painting.
Visible crew/equipment: When Kel is singing in the Orange Rain you can see stage lights reflected in his umbrella. (00:10:00)
The Raffle - S3-E3
Visible crew/equipment: When Kel is saying his balloon is handsome you can see the stagelights reflected. (00:07:20)
The Raffle - S3-E3
Visible crew/equipment: When Kenan and Kel are in the back of Rigby's, some stage lights are reflected in the fridge. (00:08:45)
Answer: Kel.