Gumpers of the Future / Planet of the Granvilles

When Gumpers has trouble sleeping Tommy suggests his "magic" pillow will make him feel like he's slept for 100 years. When he awakes, Gumpers actually believes he's 100 years in the future and he's never felt better. Can Tommy and Dinko persuade their friend to "return" to the present? /Tommy, Dinko and Gumpers are transported to an alternate dimension populated by primitive Granvilles and a giant Melba.