In Episode 128 "Double Trouble For Goku" Piccolo is seemingly possessed by Gohan for a second or two.

During the fight between Goku and Android 19. Goku Elbows 19 in the back and he goes flying into a mountain. Goku turns and looks at Android 20, who is now shocked. It then goes to Tein who thinks "That's it, Goku!" They then pan slowly to Piccolo who suddenly has a Gohan thought in Gohan's voice saying "Way to go, Dad!"...but Gohan hasn't arrived yet. Gohan, Krillin, and Yamcha are still flying to get to the battle.