say what you want about Vin, but he earns his damned pay check for those three lines. Yeah, they did some motion capture and face capture work of him according to the interviews, so it's not like he just stood around in a sound booth one day saying "Yo Soy Groot" and walked off with a couple mill.
and I totally want my own solar powered dancing groot desk toy.
and you know, it's funny. As to the end credits scene... over at the Slash Haven a few months back we jokingly postulated that between their purchases of Lucas Arts and Marvel, Disney now owned all the necessary elements to make that happen. Looks like maybe someone was listening in.