Guest Stars Chris Pratt as Peter Quill / Star-Lord Karen Gillan as Nebula Michael Rooker as Yondu Kevin Bacon as Himself Dave Bautista as Drax the Destroyer Vin Diesel voices Groot Pom Klementieff as Mantis Bradley Cooper voices Rocket Sean Gunn as Kraglin Obfonteri Maria Bakalova voices Cosmo the Spacedog