when a guy wearing briefs drops his pants and pulls his briefs up tight and narrow around his junk letting the pube-fro hang out the sides, giving a white stripe up the middle and darker fur to the sides. it works best while presenting head level to someone, by standing on a table or straddling a chair. pumping also helps.
"jimbo got up on the table in the middle of the party and sported the squirrel tail and we got kelly to turn around just in time to get a face full of squirrel tail."
A person pretending to be something they aren't, or an impostor. This is inferred because of the old alien movies where alien pods appear on earth and the "pod people" dispose of the humans and slowly reproduce the bodies, pretending to be humans.
The pod person was pretending to be my father, but I knew that he was an alien when he acted differently than my father ever would have.