Jonnie is a short shark who is light gray in color and has blonde hair. He wears a purple tank top and purple tights.
He is only seen in a flashback where Sharkface explains to SpongeBob what happened to him. Jonnie was performing a dance stunt at the Howlin Marlin, but messed up and ended up destroying the floor with his teeth and injuring himself in the process.
Jonnie is the only shark in the gang who has a hair color other than black.