Continuity mistake: When Joan is doing some sewing on her yellow dress, you can see that the ball of wool in the sewing basket next to her has nothing in it. But when Jerry puts one of the photographs inside the dress, two knitting needles have appeared. The needles then disappear in the next shot.
Continuity mistake: When Tom is placing a chicken under Spike's arm, Jerry takes a photo and you can see a trail of fake paw marks. When Jerry emerges from the dark room with copies of the photo, he takes one copy from the pile and has a look at it, but the picture shows no paw marks at all.