Continuity mistake: When Joe is first in the cat and him and 22 see each other, the cat has a harness on. In the next shot when they leave the room, the harness is gone. (00:38:20)
Other mistake: On 22's name-tag wall some of the names repeat themselves. Yossi Mizrahi and Itay Cochabi can be spotted twice, once towards the center and once towards the right side of the screen. There might be more.
Deliberate mistake: In the Spanish release, the name of the family store is written in Spanish, but inside the place it's in English everywhere. This is a very common mistake in foreign kids' films released in Spain.