The Microwave/The Meddler - S1-E17
Continuity mistake: In "The Meddler", Nicole is feeding Gumball food with a spoon and drops it on the table. The camera cuts to Darwin and then back, but the spoon is now gone.
Continuity mistake: When Gumball enters the tent of sweaty cheese, he is covered in slime. When he comes out, he is clean.
Other mistake: In "The Picnic", Darwin and Gumball bite into a rock. They each bite the rock with only two teeth each, but every one of their teeth cracks.
Continuity mistake: In "The Robot", There is a stuffed animal next to Darwin. In a few shots, the stuffed animal moves further away from Darwin by itself.
Continuity mistake: In "The Robot", Gumball and Darwin are playing with stuffed animals, which they set off to the side. Many shots later, the stuffed animals disappear.
Audio problem: In "The Robot", Gumball whimpers while his mouth is open. He whimpers again, and this whimper sounds like the first one, except his mouth is closed.
Continuity mistake: In "The Robot", Bobert shoots a laser, creating a hole in the ground. In two shots, the hole disappears.
Continuity mistake: In "The Robot", Bobert throws a pair of dice into the grass. The dice disappear in the next shot.
Continuity mistake: In "The Refund", Richard places a game on the counter in front of Larry, with the picture on the game closer to Richard. In the next shot, the game flips itself, and now the picture is closer to Larry.
Continuity mistake: In "The Gi", Nicole pulls a cord out of the wall and puts it on the ground. In a few shots, the cord is gone.
Continuity mistake: In "The Gi", Gumball and Darwin are training outside with large boombox. Later, through a window, the boombox has shrunk noticeably.
Continuity mistake: In "The Gi", There is a mailbox in front of the Watterson household. Later, when Gumball and Darwin are training in the front yard, the mailbox is gone.
Continuity mistake: In "The Gi", Penny drops a journal on the ground and does not pick it up. In a later wide shot, the journal has vanished.
Continuity mistake: In "The Spoon", Darwin and Gumball use shopping carts to open the big safe. These carts eventually disappear on their own.
The DVD/The Responsible - S1-E1
Continuity mistake: When they smash the TV something on top falls off. When the camera points back from the little sister, it's gone.
Other mistake: Nicole is through a window of the house in the scene when Darwin asked "Which one is the real Gumball?" This is probably from the episode "The Goons." (00:00:05)