Bill Belichick’s funereal demeanor is so rooted in the public imagination that any smile or moment of loquaciousness is like finding a great prize in a Cracker Jack box. You cherish little diversions like the one at Super Bowl media day on Tuesday when he talked about a hand-held monkey puppet.

For most of us, it was more fun than watching him dolefully deny the involvement of his New England Patriots in the deflation of 11 footballs used in the A.F.C. championship game. But the scandal did allow him to play Mr. Wizard by giving his summary of the effects of climate change on football air pressure.

Melancholy Bill isn’t always present, or so network production crews have found when they meet with him a day or so before each game. At times he can be downright friendly.

“Most people would assume that Belichick would be the worst,” said NBC’s Cris Collinsworth, who will call Sunday’s Super Bowl with Al Michaels. “But in many ways he’s the best.”