The pair, who led Vermont in dancing and singing during pregame warmups in the NCAA tournament game, helped the Catamounts regain their composure after falling behind by four points in the second half. Kotsopoulos tied the score with a 3-pointer midway through the second half, then Pilypaitis scored Vermont's next three baskets, including a three-point play, en route to the 64-55 win over the seventh-seeded Badgers.
"I think we were a little nervous about the lead," Kotsopoulos said. "But once we calmed everything down, we went back to what was making us successful."
Pilypaitis scored 25 points and Kotsopoulos added 14 to lead the Catamounts to their first NCAA victory in six tries.
"It's amazing for us," Kotsopoulos said. "We're very happy with it, but we want to keep going."
The 10th-seeded Catamounts (27-6) bucked the trend of the top seed winning in this year's tournament by overcoming misses on their first nine shots of the second half. The better seeds didn't lose on the opening day of the tournament for only the third time since the field expanded to 64 teams in 1994.
Wisconsin (21-11) opened the second half on a 12-0 run to go ahead 37-33. But the Badgers, who had come back from double-digit deficits three times this season, couldn't hold off the Catamounts.
"I think what happens when you have a lead is that mentally you start protecting the lead instead of playing basketball," Vermont coach Sharon Dawley said. "We knew that we had to fight back."
Alyssa Karel hit a 3 for Wisconsin to cut the lead to 46-44 with 6:38 left, but Vermont went on a 9-2 run to extend it back to 55-46. Wisconsin never got closer than four points.
"They just hit some big shots," Wisconsin coach Lisa Stone said. "I thought our defense was much better in the second half. We played our kind of defense. We settled down, but it came down to them making big shots and they hit them."
Dawley said she wasn't worried about the slow start in the second half.
"We're such good shooters that if we miss 10, we're going to start making them," she said.
Pilypaitis, who didn't attempt a shot until midway through the first half, said she just tried to stay patient.
"I just wanted to pick and choose my shots knowing that I am going to have their best defender on me," she said. "I think I was just trying to let everyone get comfortable and then pick my spots to shoot."
The game was much different from a year ago, when the Catamounts were a 16-seed and were routed 104-65 in the first round by Connecticut.
It was just the fourth NCAA tournament win in 19 tries for teams from the America East. The other wins were 10th-seeded Hartford against Syracuse in 2008, 11th-seeded Hartford against Temple in 2006 and 10th-seeded Maine against Stanford in 1999.