Curtis is a caveman that stowed away on the Diffys' time machine. He got stuck in 2004 with the Diffys and lived with them. as the series goes on he pursue a more modern attitude like cleaning his home, less grunts and more english type but his caveman instincts cause the Diffy family a trouble or two, Curtis loves rocks and knows alot about them. He is ALSO portrayed by J.P. Manoux.
- It is said by fans that Curtis could be the ancestor of Neil since they both look alike.