Erin is a female caterpillar from the episode "Food Chain." Finn and Jake meet her during the heat wave they struggle to live through when they are caterpillars. As soon as Finn sees her, he instantly falls in love. When Erin faints because of the heat, Finn and Jake take her with them. Erin explains she is out looking for food and water for her family. She faints again, but soon they find an oasis of plants and happily eat the leaves. Later, Finn asks if Erin will marry him, and Erin replies yes. However, at the wedding when they're about to kiss, two giant birds show up and begin eating the caterpillar guests. Erin and Finn try to escape, but the birds fling them skyward. As he falls to his death, Finn vows to marry her when they meet again in a different lifetime, though Erin says she might see other people when they're bacteria.
Erin is a light-pink caterpillar, with a magenta striped-pattern. Her eyes are very large and shiny, and she has three thin black eyelashes on the top of each eye. She has a big scarlet bow on her head. However, in some scenes, the bow appears pink.