Tank is a tortoise, and a pet to Rainbow Dash. He first appears in "May The Best Pet Win" (season 2), when Rainbow Dash is hosting a competition to see who is the right pet for her. She's reluctant to let Tank even take part, but Fluttershy insists, even though he fails at almost all the tasks.

In the end, the final task is a race through the gorge. Whoever crosses to finish line with Rainbow becomes her pet. However, when she damages her wing and is unable to fly, Tank allows her to sit on her back and carry her to the finish line. Rainbow decides after that to make him her pet, and names him Tank.

He's seenw earing a propellor on his shell and goggles over his eyes, so he is able to fly about with Rainbow.