 Buddy operated by Peter Elliott (adult Buddy), Lynn Robertson Bruce (juvenile Buddy), Peter Hurst, Mark Sealey (toddler Buddy), Michelan Sisti, Leif Tilden, Star Townsend, Robert Tygner, and Mak Wilson (facial controls).Buddy's vocal effects provided by Hector C. Gika, Gary A. Hecker, and Frank Welker.Rene Russo began rehearsals with the chimpanzees a month before principal photography even started.