In the short, it is shown that Gubbles has the personality and traits of a dog, including barking, fetching, growling and eating dog biscuits. He has been taught tricks by Mickey, which allowed him to escape from a cat's stomach.
Gubbles also makes an appearance in the short "No". Since Mickey can't bring himself to say no, the cat takes Gubbles away (though the fish manages to get away). Toward the end of the episode, it's revealed that Gubbles has found a girl.
Gubbles also makes an appearance in the short "Flushed!".