A Chuck flash is when you don't remember something your friends say is important, and they say ONE WORD or you see a picture, and suddenly you remember every detail of the incident. Called a Chuck flash because on the NBC show Chuck, the main character (Chuck) has a supercomputer in his brain, and all it takes to trigger a lot of important details in the supercomputer is a picture, or a name, or a face.
Jenny: Well, you know my favorite Disney movie right?
AJ: Uhm...gimme a hint?
Jenny: tick tock crocodile
AJ: -plays entire watch-swallowing crocodile scene from Peter Pan in mind- OH! Peter Pan! I just had a Chuck flash.