Brain's dog

A dog is seen with The Brain occasionally, appearing in a title card and the Season 3 episode, "And Now Let's Talk to Some Kids" in the episode-within-an-episode Brain's New Puppy. Most likely this dog does not actually exist, but is a figment of the Brain's imagination. If he is real, he could possibly be one of Pal's siblings.

Physical appearance
This dog looks a lot like Pal but has slightly darker-colored fur. He wears a blue collar with a gold pendant.