But Toews is not humorless and monotonous. He has a smile and he uses it frequently. The Blackhawks' leader can laugh, and he does so mostly at his own expense. He can handle a lot of ribbing -- and he gets it all the time from his teammates.
"There is nobody that is more fun to pick on than Johnny Toews," Hawks forward Patrick Sharp told NHL.com. "I guess I have the reputation of giving guys a hard time in the locker room, and Toews is my No. 1 target all the time."
Occasionally, Sharp said, Toews will flip out and throw a stick or smash a golf club. The captain eventually winds up laughing at himself while his teammates jump all over him.
"Maybe my nickname is getting stretched out a bit, but, hey, I don't mind it," Toews told NHL.com. "If you can make fun of yourself a little bit, then it's great."
But, and this is a big-time "but," when it comes to winning hockey, Toews is truly as serious as everyone says he is. He has been since he was a pre-teen playing for Winnipeg city championships -- and because he's still that way, the Blackhawks find themselves four wins away from a Stanley Cup.
"He's not as focused or doing a workout in the middle of the street when we're having dinner, but he's always pretty reserved and that's the best word I could use to describe him," forward Adam Burish told NHL.com. "Every once in a while we'll get him to loosen up a little bit, but he's the captain of a pretty high-profile team and he realizes that, so the image he wants to portray is important to him."
Being a serious leader is nothing new to Toews. His father, Bryan, told NHL.com Friday that Jonathan first wore the "C" on his sweater when he was a 9-year-old.
"Usually it's not a thing you do for a 9-year-old," Bryan Toews said.
Or a 20-year-old, but we'll get to that later.
When Jonathan was 9 and wearing the "C," he led his team to the city championship. They were major underdogs and everybody was wondering how they did it. They'd soon come to realize that it was because of a young "Captain Serious."
"The coach knew the boys would rally around him," Bryan Toews said. "I'm not trying to blow smoke or say how great my kid is, but he inspired the other boys to work hard. At that young age he had that quality and I was hearing that from other people, too."
"That's at least what it looked like to me and I think if you ask other people they would say the same thing," Bryan said. "It wasn't about him, though, it was about his competitiveness, his respect for others and respect for the game."
The same thing is happening today. The Hawks' level of play has gone up considerably since Toews was handed the captaincy prior to the 2008-09 season. He was, as we mentioned already, 20 years old.
"It's nuts, crazy. I mean, he's a superstar," Burish said. "If you want your kid to grow up and be someone, you want him to be like Jonathan Toews. If there was one hockey player that I'd let my sister talk to, it would be Jonathan Toews."
Chances are she'd get to talk to the relaxed version, the one that we've seen for most of the playoffs. Due to the perfect mixture of confidence and comfort, Toews has been way more forthcoming over the last few weeks than ever before in his NHL career.
But, of course, just as serious.
"I've learned what makes me a leader and how I can have success doing that and rub off on my teammates the right way," Toews said. "At the end of the day it's all about the team. Sometimes it does get a little grueling to always be thinking about what is good for the team and what will make the team win, but that's part of the job.
"If you want your kid to grow up and be someone, you want him to be like Jonathan Toews. If there was one hockey player that I'd let my sister talk to, it would be Jonathan Toews."
-- Toews' teammate Adam Burish
Toews' serious side isn't limited to hockey. His father says he's a serious golfer, a serious video game player, a serious ping-pong player.
"He's got a light side to him no doubt, but when he approaches a sport or competition, it's all or nothing," Bryan said. "He's accepting when things don't go well but there will never be any excuses from him. Ever since he was a little boy when I was involved coaching him I would say we lost to a team because they had a bigger group of better players, but he would never, ever accept that."
Toews still won't accept losing. He doesn't necessarily have to, either.
If the Hawks win the Stanley Cup, Toews will by the age of 22 (his birthday was April 29) have won a Cup, Olympic gold, a World Championship and two World Juniors. He also went to the Frozen Four twice.
If the Hawks win the Cup, there's also a good chance that Toews will win the Conn Smythe Trophy. He leads the NHL with 26 points through three rounds and brings a 13-game point streak into the Final.
"It's the fact that you hate to lose and you hate the feeling you get afterwards when you second guess yourself and ask if there is something else you could have done or we could have done?" Toews said. "Obviously life goes on. It's just a game, right? But, when it's all over you want to be the one to say you gave it everything you got.
"It looks great on paper to be a part of so many things like this so far, but I really have just gone into these games and these championships saying to myself, 'Just lay it all on the line,' because sometimes you can expose other players or teams that maybe don't want it as bad as you."
He's serious about that.
Follow Dan Rosen on Twitter at: @drosennhl