There's a little something of Bob Hope in Dr. Sid. Specifically, it's the liver spots on Sid's cueball forehead and the thick blue vein down the side of his temple. The tufts of white hair around the back were inspired by photos of Sean Connery, among many others, while the sixtysomething scientist's aged pores and wrinkles have been drawn from thousands of images of lesser-known maturing gentlemen. Donald Sutherland got away lightly; all he had to provide was Sid's voice.
Sid is an animated composite, a digital cartoon. Just keep telling yourself that when you stare into his disturbing photorealistic visage...