Quarterback Jim McMahon strolls into the Chicago Bears' interview room wearing his ultrahip, mirrored sunglasses, so it's hard to get a read on his eyes. But he seems normal. "I am normal," he claims. "In fact, I think I might be more normal than anyone else."

Well, maybe not anyone. When McMahon first turned up at the Bears' training camp in 1982, a refugee from the ultimate straight-arrow school, Brigham Young University, his fellow bruins were expecting a sterling good citizen who was maybe just a little bit boring. What they got, as the world now knows, was an anarchist, a man who rolled up that first day in a chauffeured limousine, dazzling onlookers with his trademark mirrored shades, a can of Budweiser glinting in his hand. "I think you're put here on earth to enjoy yourself," he says, grinning like a happily deranged chipmunk. "And I'm doing that."

McMahon brings that same panache to the field of play. As a quarterback he is often compared to San Francisco's nimble Joe Montana. But unlike most scrambling signal-callers, McMahon doesn't melt into the turf or mince out of bounds at the first sign of a defender in heat. He enjoys meeting tacklers head on. "I don't like the rules about you can't hit the quarterback," he was once moved to say. "Jack Lambert [the onetime Pittsburgh Steelers linebacker] had the right idea when he said to put dresses on them all. Most of 'em don't like to get hit." Not Jimbo, though. He'll even go out of his way to put a good lick on the opposition. "If I get a chance to hit somebody, I'm gonna. After all," he reasons, "they're knockin' the shit outta me all game."

McMahon brings some of that madness into the Bears' huddle. "We're loose," he says. "We get each other fired up." How? "My offensive linemen spit on me. I spit back. I come in screaming, 'Let's drive the [bleepin'] ball up their [bleep]!' " Not the motivational method favored by Dale Carnegie or Roger Staubach perhaps, but no one can argue with Jimbo's success. Not even Bears' coach Mike Ditka, who knows that giving his quarterback plays from the sidelines is sometimes a very chancy procedure. "You tell him 'Go bang, bang, bang,' " said Ditka recently, "and he goes bang, boom, boom. He shocks me sometimes, but somehow he makes it work." According to Willie Gault, the Bears' game-breaking wide receiver, playing with McMahon is an existential adventure. "It's not that the unexpected might happen," he says. "It will happen. It's crazy. Weird."

Yes, weird. Just like the haircut Gault gave McMahon in training camp last summer. Jimbo had tried to give himself a sort of New Wave crew cut but had cut perilously close to the scalp. He asked Willie to "salvage something" from the mess. Gault gave his customary 110 percent, but it just wasn't enough. "It looked pretty funny," says Willie, one of the game's most feared receivers, who is now one of its most dreaded hairstylists. In fact, it looked like the Texas Weed Eater Massacre.

There's a theory that explains McMahon's eccentricities. It holds that he is actually a blood-and-guts offensive lineman trapped in a quarterback's body. "Quarterbacks are supposed to be pretty boys," says Bear center Jay Hilgenberg, "but Jim is not that way. He's the first quarterback I've seen who acts more like one of us." Most quarterbacks hang out with their brokers; McMahon delights in Thursday night beerathons with the boys in the trenches. Before every game he has the sleeves of his jersey rolled and taped in the style of a lineman, revealing biceps that may have pumped more six packs than iron. After a touchdown he butts helmets with the men who block for him. "You're all pumped up after a score," explains McMahon. "You want to hit something, so you hit each other." But not too hard; McMahon has recently learned some restraint. "Earlier in the year we tried to knock each other out," he admits. "That was crazy."

But then mayhem has always been Jimbo's milieu. As a 6 year old in San Jose, Calif., the son of an accountant who is now a packaging company executive, he accidentally stabbed himself in the eye with a fork, leaving himself with a permanently dilated pupil—hence the ubiquitous sunglasses. At 16, he moved with his family to Roy, Utah and thence, two years later, to BYU, the Mormon school that turns out an abundance of both missionaries and pro-style passing quarterbacks. Students there routinely pledge not to touch liquor or tobacco, and McMahon was a beer-drinker and dipper of snuff. "I was on probation for most of the five years I was there," McMahon, a Roman Catholic whose mother is Mormon, has admitted. "I did some things, but a lot [of what people said] was not true. I'd go home for the weekend and come back Monday, and [coach] LaVell [Edwards] would say, 'I heard you were at a party.' I don't know who had it out for me, but somebody did."

Now, of course, with his Bears on the inside track to the Super Bowl, everybody in the NFL playoffs has it out for McMahon. And Jimbo? It couldn't bother him less. Adjusting his shades, he snaps shut his expensive leather attache case, enclosing therein no vital papers, just a nutritionist's nightmare of Cheez Doodles, Ding Dongs and sugary little fruit pies. Maybe McMahon is normal, just as he says. Or maybe, like the grizzlies at Yellowstone, this renegade Bear is what he eats.