The other half of a nice gift from those friends. Rocket I had heard of. Groot I had no clue and it appears he precedes the Marvel Universe’s launch in 1961. This does make sense though. Before Stan Lee and his skeleton crew jumped back into superhero game, the company that would become Marvel was called Atlas and it was more famous for monster stories. Len Wein said it’s why the Thing was in the Fantastic Four (a knock off of Challengers of the Unknown); if the superhero element failed, then it could have parts recycled into the tried-and-true monster genre.
Above I’m trying to do the cute little dance everyone knows Groot does during the closing credits.