Tank is introduced in the episode May the Best Pet Win!, but he's named only after being picked by Rainbow Dash as her pet. He is introduced in Fluttershy's backyard along with many other animals, and Fluttershy says he longs to be someone's pet. When Rainbow Dash arrived to get a pet, Tank made many attempts to get Rainbow's attention, but to no avail. Tank persistently tries to get Rainbow Dash to choose him as her new pet, but Rainbow Dash refuses, seeing him as a useless, slow pet that will keep her grounded.
Fluttershy convinces Rainbow Dash to let Tank participate in the competition to determine Rainbow's future pet because "he has always wanted to be a pet." He is not considered pet material at first by Rainbow, as he is slow and cannot fly, but wins her over with his tenacity. He is the only animal that helps Rainbow Dash after she gets caught in a rock slide, and not only helps her when one of her wings becomes pinned under a rock, but also gives her a ride on his back to safety. She chooses him as her new pet over the hawk that originally won, since he was the only pet to cross the finish line with her, as she had requested. This is similar to the story in Aesop's Tortoise and the Hare.
In the final scene of the episode, Tank is seen flying around with a magic-propelled helicopter rotor strapped to his shell and wearing aviation goggles, allowing him to keep up with Rainbow Dash and follow her in the air. The design of the shaft of Tank's helicopter like flying machine has been used for background weather vanes in previous episodes. Due to him not appearing in recent episodes, this has been his only appearance in the series.
Throughout the episode, Fluttershy insistently corrects others calling Tank a "turtle" to a "tortoise". Near the end of the episode, she uses "turtle" herself, and all of her friends correct her in unison. The use of either term to describe terrestrial turtles may be acceptable in some circumstances.
A Rainbow Dash toy that comes with a turtle was presented at ASM's 2011 Toy Fair, and later sold in retail. The episode was written at about the same time, about a year prior to the episode's airing.
Tank is included in the trading card set, though Pinkie Pie is accidentally identified in the "Owner" graphic. "Tenacity is a never give up, can-do attitude, and this tortoise has it!"