Sunny was a small yellow fish with orange hair who went to Freshwater High.
Sunny gave Jocktopus money on his birthday. Jocktopus, who thinks money is just worthless paper, put Sunny in a box labeled "Punch Later". Sunny was apparently saving all of the money he gave for college ("Happy Birthfish, Jocktopus").
In "Fail Fish", in the scene where Milo said that he really wanted to pass the test, up in the right, Sunny was seen getting picked up by Bud's net, meaning Bud has probably sold him to new owners.