1. Watch the episode with Dexter and Dee Dee turning into monsters.

2. Wait until the part where Dee Dee has become the white 8 legged octopus monster and Dexter is the blue giant lizard.

3. The white 8 legged octopus monster grabs the blue giant lizard by the neck and we see that the legs that grabbed the lizard have turned the color of the lizard. This lasts for a good second before the legs turn white again and the scene finishes. Somebody obviously got tired while coloring in the animation cells and goofed big time.