This show had a really overweight guy wearing dungarees in an attic type environment, it was a bit like playday... please help?

Sounds like Captain Kangaroo.
http://www.metacafe.com/watch/yt-k7cNota7aHs/captain_kangaroo_begin/
http://www.metacafe.com/watch/yt-HHRkHRpSwaM/captain_kangaroo_and_mr_green_jeans_mpeg2video/
Looking at these I think I may be wrong, I thought Mr Green Jeans had Overalls?

Mr. Green Jeans: Information from Answers.com (http://www.answers.com/topic/mr-green-jeans)
According to this, he wore overalls first, then jeans and jacket, near the bottom of the page.