Quentin Grimes was leaning on his kitchen island, snacking on tortilla chips and scrolling through TikTok. It was October 2020, and he was a couple of months away from starting his junior season of men’s basketball at the University of Houston. On his TikTok feed, he encountered video after video of people imitating dolphins and bumping their bodies into friends and strangers. Grimes couldn’t stop laughing, so he decided to jump into the deep end of the trend.

He downloaded the audio track from the app, tilted his iPhone against a toaster oven and hit record. While he was still chomping on a chip, he held his hands out in front of him, arched his back and jumped in sync with the sound of a gun firing. When two more shots from the song rang out, he sprang forward twice more, laughing as he fell out of the camera frame. The whole video lasted six seconds.

He didn’t think anything more of it until he got into bed that night and opened the app again. Within a few hours, the video had been streamed more than 100,000 times. By the next day, the number was more than half a million, and Grimes had gained 20,000 followers. It was just the ninth video that he’d posted to his account, but it convinced him that the app was where he could share the fun side of himself that basketball fans rarely got to see on the court.

“As an athlete, you want to be known for something besides just your sport,” Grimes, 21, said as he swiped on his iPhone 13 during an interview at his apartment in White Plains, N.Y. “You don’t want to just post basketball, basketball, basketball. You don’t want that to be your whole life. I think fans want to see you as an actual person.”

The Knicks acquired Grimes in a draft-night deal in 2021, about nine months after his dolphin video introduced an ever-expanding TikTok audience to his offbeat, playful personality. That charisma, as well as his penchant for the irreverent, has helped him amass more than 100,000 followers on the increasingly influential social media app, a count that trails only Josh Giddey (515,000) and Jalen Green (326,000) among the 2021 N.B.A. draft class. As a league, the N.B.A. has been quick to embrace TikTok, and its official account has nearly double the followers of the most popular sports league in the country, the N.F.L. As Grimes’s career progresses in a major market like New York, he’ll be poised to profit from his growing following. But for now, he’s more in it for the LOLs.

“I save the dunks for the people who come to the Garden,” he said. “On TikTok, I’m just trying to make people smile.”

Grimes took a circuitous path to playing for the Knicks. A Texas native, he was a consensus 5-star recruit in the Class of 2018 and joined Kansas as a presumed one-and-done player. But after a disappointing freshman year, he transferred to Houston to be closer to home. As a sophomore, he helped Houston win its second-straight conference championship and climb into The Associated Press Top 25 with a 23-8 record. Twelve days after the N.C.A.A. announced it was canceling the 2020 men’s basketball tournament because of the coronavirus pandemic, Grimes started his TikTok account. His first post was captioned: “Boreddddddd!”

As a junior, Grimes guided Houston to its first Final Four since the Phi Slama Jama teams of the early 1980s. That April, he declared for the draft but was projected as a second-round pick until a standout performance at the draft combine. In July, the Los Angeles Clippers selected him with the No. 25 pick on behalf of the Knicks, who had received the draft slot in a trade. That night, he posted a TikTok with the caption: “NEW YORK WHAT’S GOOOOD!” It received almost 500,000 views and nearly 1,500 comments.

When Ben Perkins, Grimes’s former A.A.U. coach and longtime trainer, saw the video making the rounds on social media, he gave Grimes a hard time. “In basketball, I rarely compliment him. I like to push him and prod him,” Perkins said. “The first thing I said when I saw the video was: ‘Come on, man! Who would want to look at you this much?’ But it’s really fun. It’s like his alter ego. If you only know him as a killer on the court, this is a chance to see the silly side of him.”

Most of Grimes’s posts involve him dancing, typically in a hotel room or a bathroom. Though he only posts a few times a month, he said he spends as much as three hours a day on the app and sends and receives hundreds of memes each day. If he sees a trend enough times, he attempts it. If it takes him more than a few takes, he abandons it. At Houston, he regularly included his teammates in his TikToks, but as an N.B.A. rookie this season, he thought it would be best to hold off on asking for cameos from his veteran teammates.

Early on in the season, Knicks fans saw him more on social media than on the court — he didn’t appear in 12 of the team’s first 16 games. But between those games, he was impressing Knicks coaches with his effort in practices, his commitment to studying his defensive assignments and the energy he showed even in garbage-time minutes. Grimes got his first start in December, when the team was without RJ Barrett, Obi Toppin and Alec Burks. He set a franchise rookie record with seven 3-pointers. The jersey from that game hangs on a chair in his kitchen, waiting to be framed.

“My attitude was: ‘If I only get on the court for the last minute, then it’s my goal to play 110 percent in that minute,’” Grimes said. “In one minute, you can still get a big stop or a big bucket. The coaches take note of all that. Even if you get in for eight seconds on defense, how you play is important. That was my role early. They’d say, ‘Go guard Jimmy Butler,’ and I’d say, ‘OK, I’ll go do that.’”

From Christmas through the All-Star break, he averaged more than 23 minutes per game and notched five more starts. His toughness impressed even his notoriously gruff head coach. “I love Grimes. I love Grimes,” Knicks Coach Tom Thibodeau told reporters after a January practice. “He’s a fierce competitor, can shoot the ball, can guard multiple positions, and he’s only going to get better.”

In February, Grimes partially dislocated his right kneecap when he was trying to get around a screen in the first quarter of a game against Miami. He couldn’t bring himself to look at the kneecap, adrift on the side of his leg — thinking about it even a month later sent him into a shiver — but he breathed a big sigh of relief when he learned that the injury wouldn’t be career-altering. The only lasting disappointment was that it cost him a chance to play in the same arena on the same day as his half brother, Tyler Myers, a veteran defenseman for the Vancouver Canucks. He made it back onto the court less than a month later, but he’s taken it slow as the Knicks season ends without a playoff berth.

He’s also slowed down his posting during his recovery. But that doesn’t mean he’s spending less time on social media. Every night, after he’s taken a shower and turned off all the lights in his apartment, he puts his phone in his hand and his head on his pillow. “It’s just me and the brightness of the screen, scrolling and scrolling,” he said. “You get hooked” — he snaps his fingers — “like ! And then you’ve got to force yourself to go to sleep even though you’re not tired.”

With his rookie season almost behind him, Grimes has big plans for his future in New York — on the court and online. He said he wants to do more videos next season with Barrett and Cam Reddish, whom he has known since they were sophomores in high school. And, of course, he hopes that as a healthy group, they can help steer the Knicks back to the postseason. “Next year,” he said, “people are really going to see what we can do.”