The Treehouse Handshake/The Big Pictures - S3.E18

Sally invents a secret treehouse handshake, but Nick cannot remember the sequence. Cat takes them to Over-and-Overton, where they figure out how to get through a series of obstacles by recognizing patterns.

Nick and Sally do not understand why one toy car goes faster than another. The Cat says he needs their help to move some big pictures and along the way, they find out about how to make things more aeordynamic.