Guardians of the Galaxy 2 said both hello and good-bye to Baby Groot as the post-credit scene revealed Baby Groot had grown to Teen Groot.
At the D23 Expo and Comic-Con, Marvel Studios released The Avengers: Infinity War trailer where Cinema Blend noticed that the Groot in the footage looks a lot like Teen Groot from the Guardians of the Galaxy 2 post-credit scene; so they asked director James Gunn about it, as Gunn is also producing and helping out with the Guardians scenes in Avengers: Infinity War.
"He's exactly the same," James Gunn confirmed along with confirmation that The Avengers: Infinity War takes place about four years following Guardians of the Galaxy 2, which explains Teen Groot. "That's exactly the Groot we designed for Infinity War."
Not much is known about Teen Groot other than what was shown in the Guardians of the Galaxy 2 post-credit scene, but he did seem like your typical teenager with a messy room, addicted to his tablet and being "scolded" by his "parent."
Watch the scene:
Teen Groot is also featured in the Avengers: Infinity War poster where he definitely looks like an adolescent as well:
The Avengers: Infinity War hits May 4, 2018.
As the Avengers and their allies have continued to protect the world from threats too large for any one hero to handle, a new danger has emerged from the cosmic shadows: Thanos. A despot of intergalactic infamy, his goal is to collect all six Infinity Stones, artifacts of unimaginable power, and use them to inflict his twisted will on all of reality. Everything the Avengers have fought for has led up to this moment - the fate of Earth and existence itself has never been more uncertain.