The gator appears only in Attack of the Alligators!, at the very end of the episode, when Tin-Tin asks Alan to look at something in the bathroom. She then tells him to shut his eyes, and when he opens them, he finds there's an alligator in the bath tub. Tin-Tin tells him he said it'd be nice to have a pet, so she got it him for his birthday (which isn't until the day after).
Despite facing alligators grown to monstrous proportions earlier on in the episode, Alan manages to laugh it off.
Although it is unknown what became of the creature, it is noteworthy that in the movie Thunderbirds Are Go, a stuffed alligator is seen on the floor of Alan's bedroom.
- As usual, the "alligator" is in fact a baby crocodile.