Fans are used to seeing guest judges filling out the America's Got Talent panel, but country musicians are sorely underrepresented on the show.

So far only Reba McEntire and this week's guest judge, Martina McBride, are the only two country singers to take the show's fifth seat.

But McBride's episode is destined to be a classic, because she gave the show's top honor to a pair of incredible performers.

"In a million years, I never thought I would be here today."

In their audition, ballroom dancers Quin and Misha impressed the judges before they even danced a single step.

Quin is 71, while her partner Misha is just 35. But their age difference is just a small part of what makes Quin such an incredible performer.

"In a million years, I never thought I would be here today," she told the judges.

"I grew up in a small village in Thailand.  My father was a rice farmer. We were very poor, but my parents taught me very, very hard work and I learned not to give up."

"I met my husband Rick 46 years ago, so I came to America and I am so grateful every day to live in this country. I still appreciate it so much."

Surprisingly, Quin didn't start dancing until she was in her 60s, and convinced Rick to take a class with her.

"It was amazing. I have never experienced anything like it in my life. I realized it was my dream."

After just a few years, Rick "couldn't keep up," but he encouraged Quin to keep pursuing her passion, and it led her to the Judge Cuts round on AGT.

"We were not even sure we could fly the next day and perform."

What you don't see in video of Quin and Misha's latest performance is the injury that almost ruined their chances.

"A lot of people don't know this, but four days before, Quin injured her foot," Misha revealed to Good Housekeeping.

"I accidentally stepped on her foot and her toenail came off and started bleeding."

After spending four hours in the E.R., Quin's injury was still so serious that the pair thought they would miss the show.

"We were not even sure we could fly the next day [for the audition] and perform, but we did, hoping it would heal," Quin said, but she wasn't about to miss her big chance.

"It was bleeding really bad, but I taped it tight. It really hurt and was raw for a few days," she remembered.

"I told myself, 'This is an opportunity that only comes once.' So I pulled myself together and told myself not to think about it."

Quin admits that by the end of her performance there "was blood all over" her foot, but she still blew away the judges and the crowd.

"You say you want to inspire people of a certain age, but you inspire everybody of all ages."

The judges had nothing but praise for Misha and Quin, saying that their routine was impressive at any age.

"You have absolutely inspired me," Heidi Klum told them. "I think you are an incredible woman. I love what you do. I love watching you guys. I am very impressed."

"Every time you come on you light up the stage. It's great," Simon Cowell agreed. "It's what we are looking for."

McBride didn't hesitate to slap her Golden Buzzer for the talented dancers, sending Misha and Quin straight to the Live Rounds.

"You say you want to inspire people of a certain age, but you inspire everybody of all ages," the singer told them. "It was truly a remarkable performance. I don't know. It really moved me. I think it is incredible."

"There are so many people who give up at a certain point in life. I really think that that message is something people can benefit from hearing."

The Golden Buzzer moves Misha and Quin one step closer to winning the $1 million grand prize, and the show's crankiest fans will be happy to see a non-singing act get put through.

But McBride also had praise for the musical trio We Three - made up of siblings Bethany, Joshua, and Manny - who gave a moving performance dedicated to their late mother.

She said their original song "Heaven's Not Too Far" had "one of the best first lines I've ever heard."

"It was just so vulnerable and real, and I think that people need to hear that song and more from you guys."

We Three were put through to the Live Rounds, which will begin after one final episode of Judge Cuts next week.

Who are you rooting for to win the $1 million prize this season?

Here are more talented acts you should see:

• Youngest AGT contestant ever stole the show with her Sinatra cover.
• Incredible aerial performers with a Golden Buzzer for their jaw-dropping performance.
• Deaf singer moves the audience to tears on AGT, then gets the Golden Buzzer.

[H/T: Good Housekeeping, USA Today]