Closely related to "attention deficit… ooh, shiny!" This meme usually appears in audible communication. It's not easy to convey visually, because the timing is important.

The meme appears when someone is explaining about their supposed adult attention deficit disorder, and halfway through the description, they exclaim "Squirrel!" referencing the dog from Disney's Up.

The reason this doesn't work as an example of "ooh, shiny!" is that there is almost never an actual squirrel present. Even people with ADD require some stimulus to divert their attention, but in the case of this bit, the stimulus is the conversation itself. The speaker needs an out, a way to end a very boring statement about a medical condition. Someone capable of this level of comedy is not very good at comedy, but more importantly, is very unlikely to actually have any form of attention deficit disorder.