The Mothers - S3-E17
Plot hole: When the "refrigerator" falls on Tobias's mom, the boys are watching from a side view. It is later revealed that the fridge was just a cardboard cutout. The boys were watching from the side, so how did they not notice it?
Continuity mistake: When Gumball and Darwin board the bus, the bus driver pulls out an axe and the boys ask what it's for. The driver says he uses it to push the pedals and he is still holding it. In two shots, the axe has vanished.
Continuity mistake: The Kids are playing cards on the floor, with some cards in their hands and in a pile on the floor. Right before The Kids stop playing, the cards on the floor disappear.
Continuity mistake: Penny is looking next to the corner of a wall next to some lockers. In the next shot, she is now next to her locker, which is not that close to the corner she was just standing next to.
Continuity mistake: Nicole arrives in front of The Pest control bug and steps out of the car. In the next shot, she is suddenly over the barrier, even though she did not previously step over anything.
Continuity mistake: Gumball enters a bathroom where Banana Joe's father is taking a bath. At first there is nothing behind Banana Joe's father. In the next shot, two bottles of shampoo appear behind him. In the next shot, the bottles disappear again.
Audio problem: When Penny turns into a dragon, she begins to say something, but her speech goes faster than her mouth movements.
Continuity mistake: Gumball pokes his tongue through a newspaper that Darwin was holding. In a few shots, the newspaper disappears.
The Allergy - S3-E16
Continuity mistake: The school nurse drops a pencil right next to herself. The pencil disappears in two shots.
Continuity mistake: A man breaks through the windshield of his car, spreading glass shards everywhere. In a few shots, The Man is still on the ground, but the glass shards have disappeared.
Continuity mistake: Gumball and Darwin are standing next to an open locker next to Tobias. The camera cuts to Tobias, and then back to the boys, but the locker is now closed.
Continuity mistake: Gumball and Darwin break through Mr. Robinson's fence, leaving some scattered pieces. In a few shots, the pieces are gone.
Continuity mistake: The Wattersons are listening to Gumball's conversation through the door, and Nicole is using a drinking glass. In a few shots, Nicole does not have the glass, nor is it on the floor.
The Downer - S3-E37
Continuity mistake: Gumball is being overtaken by the darkness, and there is a coffee table in front of him. When he escapes the darkness in a few shots, the coffee table is missing.
Continuity mistake: Gumball is sitting at the dinner table, and a pile of food is next to his plate. Two shots later, the food disappears.
Other mistake: Penny's hand is smaller than her eye, but manages to completely cover it.
Continuity mistake: Gumball is on stage at a play. He is saying his line and facing away from the audience. In the next shot, he continues his line, now facing the audience.
Continuity mistake: Nicole punches the number pad of a telephone receiver, damaging it. Later, Anais picks up the same phone receiver, but the number pad is fixed. No one but Richard touched the phone in the meantime, and he did not fix the phone, either.
Continuity mistake: A man drops a DVD case in the video store. Two shots later reveal an empty store with no DVD case on the ground.
Continuity mistake: Richard's flashback shows him throw money onto the counter. In the next shot, The Money disappears.