Continuity mistake: The letter D scratched into the pop up book is in white when first written. When shown again later, it's written in black.
Factual error: After breaking out of prison, Paddington contacts the Browns using his 50p coin to make the phone call. It is actually 60p to make a public phone box call in the UK.
Continuity mistake: The amount of ketchup and mustard on the prison chef's apron changes between shots.
Plot hole: It was said that Paddington was caught red-handed robbing Gruber's store however there is no evidence to prove this and most of all the stolen item; the pop up book wasn't in Paddington's possession.
Suggested correction: There is evidence to make people believe he broke in. The evidence that he was in the building confirmed that he "broke in", and Phoenix's testimony that no-one else was there was enough to convict.
Continuity mistake: After Paddington shaves the judge's hair he smashes himself against the shop window. The amount of hair shaved is much less than in previous and further shots.
Deliberate mistake: Paddington puts a red sock in the load of prison clothes which turns all their clothes pink. However, it was a single red sock in the "uniforms" machine, but in the next scene the entire prison is wearing pink clothes now. The machine is nowhere near big enough to wash all the uniforms at once - the pile we see is huge.
Continuity mistake: Paddington gives chase on 'dog back' to the thief after he has stolen the book from the antiques shop, catches up with him, but the thief drops a smoke bomb and disappears. The dog is in shot as Paddington talks to the thief, but when the smoke bomb is dropped we get an aerial shot of the whole area and there's no sign of the dog.