Watch towards the end of the episode "Steve", when the babies left Steve in the sun and Didi brought them in to get hot chocolate. When it shows the babies at the table close-up, they have different cups. Tommy has a red one with a pine tree, Chuckie has a blue one with a snowman, etc. When it zooms out, look at their cups. They all look like Tommy's cup, but then when they zoom in again, they're back to the original colors!!