Frankie is a character who appears in the episode "It's a SpongeBob Christmas!"
He is a short indigo fish wearing a black winter hat, a brown sweater, and dark blue overalls. He also has grouchy eyebrows and a five o clock shadow from the Jerktonium he consumed.
Role in episode
When Johnny sarcastically tells him "Merry Christmas" while under the effects of the Jerktonium, Frankie (who is also under the effects of Jerktonium) then throws a snowball right into Johnny's face making SpongeBob worried that Santa will skip Bikini Bottom.