A ridiculous premise turns into a pretty good comic: Dr. Doom body switches with Daredevil! A multi-issue epic that ends in the pages of F4, with guest shots by just about everyone.
This really felt like an extended annual. Fun, though.
Creators: DD: Stan Lee and Gene Colan; Fantastic Four: Lee and Kirby
For the complete history of the MU, year by year, go here.