America's Got Talent: Simon Cowell presses the Golden Buzzer for aerialist Sebastian after his partner was injured

Simon Cowell pressed his Golden Buzzer for aerialist Sebastian, who performed alone after his partner Sonia was injured, during Tuesday's two-hour episode of “America's Got Talent” on NBC.

After the accident during rehearsal, Sebastian declared that he would not give up on his dreams and performed solo, rising high above the stage and spinning around, propelling himself using only his body weight.

Sonia, whose arm was in a sling after the accident, watched him backstage. When he finished, the audience and the jury gave Sebastian a standing ovation.

“I'm standing up because a lot of people would have given up,” said Simon, 64. “I think most people would have said we've had an accident and we can't carry on. They did the opposite and carried on. Not only that, I'm not saying that just because of that, not just because of that, that was by far the best reaction we've had so far, that's why you get…”

Then Simon reached out and pressed his Golden Buzzer while Sebastian hugged Sonia in disbelief.

Simon came on stage to congratulate them as golden confetti fell around them. Sebastian said he only had three days to organize the act.

“That's the definition of courage,” Simon said. “You don't give up.”

Brent Street, a dance group from Sydney, Australia, opened the show, part four of the quarter-finals. They hoped their performance would be good enough to move on to the next round. Simon Cowell fanned himself with cue cards as he watched their intense synchronized dance routine.

“Unbelievable!” said 68-year-old Howie Mandel.

“That was spectacular!” said 52-year-old Sofia Vergara.

Simon said that he would not press the Golden Buzzer for her because he found her performance a bit artsy and slow at the beginning.

Next on stage were acrobats Illya and Anastasiia Strakhov, who had traveled from Ukraine to perform on the streets of Las Vegas. Illya surprised the crowd by doing a headstand on three bowling balls high up on a rickety glass and plexiglass stage. He finished the act with a handstand, balancing on just his finger in a champagne bottle.

“I think you're fantastic,” said Heidi Klum, 51. “You've put on a show that really keeps us on the edge of our seats.”

Sonia and Sebastian were delighted with the jury’s praise

“I'm standing up because a lot of people would have given up,” said Simon, 64. “I think most people would have said we've had an accident and we can't carry on. They did the opposite and carried on. Not only that, I'm not saying that just because of that, not just because of that, that was by far the best reaction we've had so far, that's why you get…”

Sonia, whose arm was in a sling after the accident, watched him backstage

Sebastian whirled around high above the stage during his number

Howie Mandel, Heidi Klum, Sofia Vergara and Simon gave Sebastian a standing ovation after he performed solo

Simon told them, however, that he didn't think they were doing a Vegas gig and that it seemed too small to him.

“I’m disappointed,” said Simon.

Next, 16-year-old singer Oscar Stembridge from Sweden took the stage and performed one of his own songs. When he finished, the entire jury applauded.

“Oscar, I think you're already a superstar,” Sofia said. “You're incredible.”

“I think you're a star,” said Howie. “To be honest, I think you picked the wrong song.”

Heidi said she wished he would let his voice flow and show them more range.

“In my opinion, you're like a little diamond,” Simon said. “I'd love to work with you. I really mean that. There are just not many people like Oscar. There's something really cool about you. You know who you are. And I just have a really great feeling about you.”

Magician and comedian Jonathan Burns of Lancaster, Pennsylvania, came out in a straitjacket and asked host Terry Crews to put him in a sofa bed and close it. He told Terry to put the cushions back on. Simon rang the bell. Jonathan was not in the sofa when it opened, but came out of an armchair.

Brent Street, a dance group from Sydney, Australia, opened the show, part four of the quarter-finals

Next, 16-year-old singer Oscar Stembridge from Sweden took the stage and sang his own song

“Oscar, I think you're already a superstar,” Sofia said. “You're incredible.”

Sofia called the performance entertaining.

Next, L6, a family singing group from the Philippines, took the stage. They said they wanted to win so they could buy a big house for their large family who now lived in a cramped house. They took the stage all wearing red suits and sang “Rewrite the Stars” from The Greatest Showman.

“I think your voices are spectacular,” said Sofia. “I really enjoyed listening to you.”

Simon told them that they were very good singers and that he gave them a real chance to make it.

Comedian Tonikako from Tokyo, Japan, joked about “wearing pants.” He struck various poses in his swim trunks and it looked as if he was wearing nothing.

“Don’t worry, I’m wearing pants!” said Tonikako.

“You are like a gift that always brings joy,” said Sofia. “It's great fun!”

“They're one of my absolute favorite acts,” said Simon. “They're really silly and funny.”

“They have the ability to do so much with so little,” Howie said.

Singer Stephanie Rainey from Cork, Ireland, performed an original song called “Woman,” which she said she wrote when her mother was diagnosed with cancer. Stephanie said she was very lucky that her mother pulled through.

Comedian Tonikako from Tokyo, Japan, joked about “wearing pants.”

“Stephanie, your voice is so incredible,” Sofia said. “It was very moving.”

Howie didn't like her song as much as her first song.

“I can feel how much this means to you,” said Heidi. “I think you're great.”

Simon said he didn't think this song was as good as their first song, but he thought it was good enough to get them through to the next round.

Next, Boston comedian Erica Rhodes took the stage and joked about her funny voice, saying she doesn't like dating and likes being put in the “friend zone.”

Singer Stephanie Rainey from Cork, Ireland, performed an original song called “Woman”

“You're so real, so funny, so relaxed,” Howie said. “Your voice is enchanting.”

Heidi said she could imagine them in Vegas. Sofia said she could imagine them in a sitcom. Simon said he wasn't thrilled.

The quick-change artist Solange Kardinaly from Portugal thrilled the audience with her magical outfit changes in the blink of an eye.

“You didn’t disappoint,” said Heidi.

“That was perfect,” said Sofia.

Simon told her she had something special and said she had a Vegas gig.

Ten-year-old Pranysqa Mishra from Tampa, Florida, closed the show with a blaring performance of Miley Cyrus’ hit “Wrecking Ball.”

Ten-year-old Pranysqa Mishra from Tampa, Florida, closed the show with the Miley Cyrus hit Wrecking Ball

“I mean, the best comes last,” said Heidi. “You did such a great job!”

“You sounded incredible,” said Simon. “That really surprised me.”

“America's Got Talent” returns on Wednesday with the results of the audience vote and three acts will advance to the semifinals.

The semifinals will air on NBC on Wednesday, September 11.