This was one of the last major projects from Bill Cayton and his team. They were trying to "merge media" in a way to expand on the original Czech film. "Journey to the Beginning of Time" is a collage of live action melded to 2D and 3D modeling, with puppets in select shots plus stop-motion animation. And yes, there's cartoon animation, but you have to look close!

Remember, I haven't seen the entire film in about 50 years but I'm impressed by the artistry that Bill and Fred brought to the table to make this series. If you are able to find the entire film, notice the lively dialog between the four boys. The writing team outdid themselves. From what I remember, the boys are informative without mocking each other and the language used matches the action in each scene appropriately. 

If you are able to locate a restored full-movie version it might make a good R-D Theater Feature!