Frank is a muscular goldfish, usually seen hanging out at Goo Lagoon, where he first appears in the episode "Ripped Pants."
He is very muscular. He is a bronze-brown colored fish with dark salmon colored lips. In some episodes, he has sort of "squinty" eyes, unlike the ones shown here. He is orange in "Welcome to the Bikini Bottom Triangle." A blue version of Frank can be seen in the level "Krusty Krab Alley" in the game Super Brawl 3.
Much like Larry the Lobster, Frank appears to be serious about his physical appearance. This was shown in "Bubble Buddy" when he turns bright red and walks away ashamed when he thought SpongeBob told him to shake his "bubble butt" (he was really referring to Bubble Buddy). He also appears to be a coward as shown in "The Fry Cook Games" when he was desperate to leave the arena. He even seems to have anger issues when it comes to relationships.