In 1976, an evil alien scientist recreated a number of long-forgotten monsters...
...to battle his old foe, the Incredible Hulk...
...including...awww, you guessed...
The never-reprinted story from Incredible Hulk Annual #5 (1976), written by Len Wein and illustrated by Sal Buscema and Jack Abel was a tribute to the 1950s pre-superhero monster stories Stan Lee and Jack Kirby produced in astounding amounts for Marvel's predecessor Atlas Comics.
Besides Groot, five other classic monsters with silly names appeared...
...including the alien scientist (and monster), Xemnu, who re-created the other aliens!
BTW, Xemnu was originally-known as "the Living Hulk", so when his pre-Marvel stories (he appeared twice!) were reprinted in the late 1960s (after the introduction of the green-skinned Hulk), he was re-named "the Living Titan".
Technically, this was not the "real" Groot, but, it's still considered the character's first appearance in the Marvel Universe...as well as confirmation that some (if not all) of the pre-superhero stories are part of the history of the fictional universe.
