Marvel Groot thermoactive mug. Groot is a fictional character that appears in American comics published by Marvel Comics. He was created by Stan Lee, Larry Lieber, and Jack Kirby and first appeared in Tales to Astonish #13 (November 1960). Groot is an alien creature resembling a tree. He was originally an invader whose goal was to capture humans and use them for experiments. The character was reintroduced in 2006 as a heroic noble being and appeared in Annihilation: Conquest. Additionally, Groot became one of the main characters in the film Guardians of the Galaxy and joined the team of the same name. Product under official Marvel license. A great gift for any Marvel fan.