Oklahoma played catch-up for most of the night, trying to chase down the latest No. 12 seed looking to create some March chaos.
The fifth-seeded Sooners finally caught North Dakota State, and then failed to hold on.
"Our guys fought like crazy, last 25 minutes of regulation, to get back and finally get into a position to win the ballgame," Oklahoma coach Lon Kruger said. "They hit a big shot to get it into overtime. Tough, tough one to lose."
Lawrence Alexander hit a 3-pointer with 11 seconds left to force overtime and freshman Carlin Dupree scored four points in the final 75 seconds as North Dakota State knocked off Oklahoma 80-75 Thursday night.
The Bison (26-6) picked up their first NCAA tournament win by rallying in the final minute and then outlasting the Sooners in overtime. Alexander finished with a career-high 28 points, but it'll be his falling-down, fist-pumping celebration after the tying 3 that will be replayed in Fargo for years.
And it'll be part of nightmares in Norman after the Sooners rallied to take their first lead of the second half with 1:29 remaining.
"I don't know who was on the ball, but he made a big shot, a big 3," Oklahoma's Cameron Clark said. "We thought we had him contained. He stepped up and made a big shot and tied the game."
Clark led Oklahoma (23-10) with 25 points, including 16 in the final 5 minutes of regulation and overtime. Clark was the catalyst of Oklahoma's late run that gave the Sooners a 65-61 lead with 38 seconds left in regulation. Isaiah Cousins added 17 points and Jordan Woodward had 13, making up for leading scorer Buddy Hield being limited to nine points on 4-of-14 shooting.
Oklahoma gave NDSU a chance at tying by twice missing foul shots in the final minute. Woodward split free throws with 39 seconds left and Cousins did the same with 26 seconds remaining, giving the Bison a chance to tie it.
Oklahoma had chances to win in regulation. With the entire lower bowl standing, the Sooners got off three shots. Hield's open 3 rimmed off, Woodward's free-throw line jumper was short and Cousins' reverse layup attempt at the buzzer never caught the rim.
"It's upsetting to miss them three shots, but we were still pumped up to go into overtime," Ryan Spangler said.
So were the Bison.
NDSU scored the first four points of the extra session on baskets by Marshall Bjorklund and Alexander, but Clark's 3 pulled Oklahoma even at 70. Taylor Braun put the Bison ahead 72-70 with 1:39 left on a driving layup. After he fell to the court, Braun got tangled with Clark, who appeared to inadvertently kick Braun in the face. No additional fouls were called, but Braun fouled out seconds later reaching in as Clark attempted to shoot.
Clark hit both, but 4 seconds later Dupree — a 58 percent free throw shooter — hit a pair to put the Bison back in front. Following an Oklahoma miss, Dupree drove baseline and scored instead of running off time. It was the shot of an inexperienced freshman, but coach Saul Phillips didn't mind. It put the Bison up by four and started the celebration.
"It's harder to be them than us in this situation — it is. It's harder to be a 5 than a 12. I was at Wisconsin as operations guy. I've been on the other side of it. It's hard," Phillips said. "If we lose, everybody would have been disappointed back home for a night, and then they would have talked about how great of a season we had."
TrayVonn Wright added 14 points and Bjorklund scored 13, including a hook shot to open an overtime session in which the Bison never trailed. Braun, his body beaten up throughout the game, finished with 11 points and six rebounds before fouling out.
This trip to the NCAAs was part of a surprise season for the Sooners that relied heavily on their youth. That gives Oklahoma promise for the future.
"In the short term this is extremely disappointing and hard to experience," Kruger said. "But they like to play, they will continue making progress and we'll get back to work and try to get better."