I remember one afternoon in the 1970's this was on to replace the scheduled program for that time slot. It starred Ike Eisenmann (Return from Witch Mountain, Star Trek: The Wrath of Khan) and Lance Kerwin (Salem's Lot, Enemy Mine) It was made in 1976 as one of the ABC Afterschool Specials. I can't remember much about it but one thing that does stick in the mind of people who did see it, is the phrase "You can do it, Duffy Moon!" The other thing is when he thought this phrase he would puff up his cheeks. Now the US readers of this Blog might remember this more than the UK ones, though I have over the years met a few close mates who did remember this show. In fact a search of forums seems to reveal a lot of people out there who thought they were the only one who ever seen this show, so there's probably more people seen it than I thought !
Shorter in stature than most of his classmates in the sixth grade, young Duffy decides to purchase a somewhat mystical book that, according to its advertising, will enable him to "THINK BIG." Among the book's suggestions is to speak in a robotic voice when confronted by an adversity (namely, the school bully). An unexpected incident involving an injured pet crow serves to prove that Duffy doesn't really need a book to tap the inner resources -- and strengths -- that he's had all along.
You can do it, Duffy Moon!