Kevin Garnett was introduced to a rousing ovation from the TD Garden crowd. He threw down a dunk in the first quarter and scored nine points in the first nine minutes.

He did all the little things that have been missing from the Celtics these past few weeks and he fought through foul trouble to help them get a much-needed 98-95 overtime win over the Trail Blazers.

But Garnett wasn’t truly back until he cracked his first joke in the postgame press conference, likening his body to a 76 Ford Pinto. As much as the Celtics missed his energy and intensity on the floor, they also seemed to be missing his sense of humor.

These have not been fun times around the Celtics lately. Players have been tense, irritable and moody. It’s January in the NBA and these things are bound to happen everywhere, not just in Boston. But the Celtics particularly have been angry, and not in a constructive way, either.

“Especially with the way we’ve been playing, we’re definitely happy with the win,” Paul Pierce said. “We definitely know we can play better. It’s going to come. Getting Kevin back there was great having an emotional leader, we fed off of that from start to finish.”

Through the losses and the fines something has been missing from this team since the new year. It’s too easy to say that it’s all about Garnett, but it certainly felt that way Friday night, and for one night at least the team that we have known these last few years was once again recognizable.

Here are the three things we learned from last night:

THE KEVIN GARNETT DIFFERENCE

Coming out of a timeout in the fourth quarter, Garnett went body to body with Portland’s LaMarcus Aldridge way before the ball was set to be inbounded. Aldridge turned to the baseline official with his arms up as if to say, “Seriously?” Yup.

Garnett’s entire game is predicated on making people on the other team uncomfortable, while also providing a comfort zone for his teammates. Garnett continued to jostle with Aldridge and when the shot caromed off the glass Garnett threw his body into the fray with his old reckless abandon.

Two or three times it ticked off various hands before landing safely in the Celtics possession. Garnett winced and seemed to hobble for a moment and there will be countless more times when these situations play out and everyone holds their breath. But if Garnett is going to be the player he was, the player the Celtics need, that’s just the way it will have to be.

“I got banged a couple of times,” Garnett said while unveiling the Pinto analogy. “But I’m OK, man. I’m all right.” 

Garnett allowed that his timing was off in regards to rebounding and his usual automatic jumper was also out of rhythm, but he found a way to contribute 13 points and four rebounds in 30 minutes in addition to everything else.

“You look at all the superstars around the league he does most of the things that the other superstars don’t do,” Pierce said. “The way he talks on defense. The way he helps everyone on the court. The way he sets screens. Those are things that are really overlooked around the league. He’s so selfless. One of the most selfless players to ever play the game.”

Garnett is not happy when he’s not playing. That seems like an obvious statement on its face, but for Garnett the last few weeks have been stressful.

“It was very difficult sitting out watching,” Garnett said. “I don’t sit on the bench for a reason. I’ll go to guys individually and give them my take on the game. You’re almost helpless. That’s the word I’ll use.”

Helpless has been an accurate description for the way the Celtics have played at times in his absence, particularly in the second half of games when they have had the lead.

“We know we’ve dropped too many games over the last few weeks,” Rasheed Wallace said. “We just had to go out there and play, especially in the third quarter. Tonight it wasn’t the best third quarter but it was a little better then we’ve had.”

They blew another advantage against Portland, but the difference this time was they found a way to claw their way back into it, and it’s easy to conclude that Garnett was a big reason for it.

GARNETT’S EFFECT ON THE BENCH

Wallace has had good games and he has had games he’d rather forget while starting for Garnett. But it hasn’t just been Wallace’s play as a starter that has affected the Celtics. It has also been his absence from the second unit that has had a ripple effect on everything they do.

Wallace turned in a 14-point, six-rebound effort coming off the bench, which was exactly what the Celtics had in mind when they signed him last summer. They also had strength in numbers, which became very important when Garnett, Kendrick Perkins and Wallace all encountered foul trouble.

It wasn’t just Wallace. Tony Allen also had a strong game with eight points in 24 minutes and one of the biggest plays of the night when he finished off a loose ball scramble with a dunk in the overtime session.

Wallace declared later that Allen deserved the game ball for the way he played defense on Andre Miller and in replacing Pierce who fouled out at the end of regulation.

“The biggest plus to me, and it happened in the first half, is our second unit is alive again,” Doc Rivers said. “Bringing Rasheed back to that unit you can see they have life again.”

With Wallace on the floor with Eddie House the spacing that has been missing the last few weeks returned, as well. 

“If you look at the rotation, when Rasheed comes in he spreads the floor,” Ray Allen said. “He’s playing with Eddie and Eddie’s getting shots from Rasheed. The way they moved the ball around, Eddie’s getting easy looks. That’s a big difference.”

RAY ALLEN SAVED HIS BEST SHOT FOR LAST

In the midst of what several observers felt was his worst shooting night in a long time, maybe ever, Ray Allen caught the ball at the top of the key down two points with less than a minute to play in overtime.

For Allen, who had made just two of his previous 13 shot attempts and inexplicably had missed two free throws, the next shot was no different than the ones that had preceded it. This has always been the case for Allen who has survived this long as an elite shooter by focusing more on the process than the results.

Allen didn’t hesitate. Why should he? He’s only done this thousands of times before in games, and probably millions of time by himself in practice. The shot was pure and the Celtics had the lead.

“Ray is one of the great shooters of all time,” Pierce said. “He’s right behind me. I told him in that huddle. We told him, ‘Keep shooting, Ray.’ Coming off the very next play he had the wide-open look. That’s what we expect from Ray. We believe in him that much no matter how his night is going.”

True to form, Allen focused on the process when asked to detail his night. 

“What was interesting for me this game, I don’t think I took any [perimeter] shots in the first half,” Allen said. “I missed two layups. My rhythm wasn’t really established. It still looked good. It felt good when it left my hand. It just was not going in for me. It was frustrating but I still just think about the next shot. It was just one of those days where I felt slightly off.”

That, as Rivers said, is what separates the great from the merely good. No one felt differently either.

“[Rajon] Rondo turns to me and says, ‘You know Ray’s going to be wide open on this,’” Rivers said. “And I’m like, ‘Yeah, that’s the idea.’ Ray’s a shooter and you’ve just got to keep shooting.”