The Masked Singer Solves Season 5's Biggest Mystery with Quarterfinals Unmasking

This post contains spoilers from Wednesday's episode of The Masked Singer.

The Masked Singer quarterfinals took place Wednesday and by the end of the night, viewers got an answer to one of this season's biggest mysteries: the number of singers inside the Russian Dolls.

Russian Dolls started the night out by tackling Elton John's "I'm Still Standing," complete with oversized rectangular frames and feather boas. But the dolls considered themselves superfans of Weird Al Yankovic. "He's literally given us great direction in our lives," they said in their clue package for their superfan super clue.

Michael Becker/FOX

After each performance, host Nick Cannon brought out a piece of fan mail each undercover celebrity received. Russian Dolls' letter read: "I was a fan of you individually, but when I saw your band together in person — wow! Like, I can't even. Love you to the moon and back again."

Panelists Ken Jeong, Jenny McCarthy, Nicole Scherzinger and Robin Thicke, joined by comedian and actor Rob Riggle, guessed groups Barenaked Ladies, Devo, Hanson and Savage Garden could be under the many Russian Dolls.

Black Swan went next, revealing in their clue package that they "had some disappointments in my career." "It made me frightened to take risks, so I made a resolution to say 'yes' to things that scare me," the feathery fowl continued. Black Swan also shared their connection to Cher in the clip: "We've both been a part of iconic fantasy films and she was a part of my world the very first time I shared my voice."

Michael Becker/FOX

The majestic bird then put their own spin on Ed Sheeran's "Thinking Out Loud." "You just killed it," said Scherzinger, 42.

Black Swan's piece of mail stated that the covert singer once appeared on The Oprah Winfrey Show and "was so excited to have gotten the major recognition" they deserve. The panel suspected Black Swan might be pop stars Dua Lipa or Normani.

Piglet opened their version of "Superstition" by Stevie Wonder with some opera singing — a Masked Singer first. In Piglet's clue package, they said their "little piggy" wanted them to dress as a pig on the show. Piglet also called Bruce Willis their "all-time idol." "I was speechless when we met," the swine said. "Always cool to meet a fellow action star."

Michael Becker/FOX

Piglet's mailbox featured a fan letter littered with clues. "Whether on my TV or in my headphones, I'm so lucky I discovered you in the '90s, but I've never been jealous of your public relationships," the note read. "P.S. I drew your picture."

The judges suggested boy banders Nick Lachey and Justin Timberlake, as well as action star Jeremy Renner.

Yeti brought the chill with Rascal Flatts' "Bless the Broken Road." But in Yeti's clue package, he named rap legend Diddy, "who I've been lucky to work with," for his superfan super clue. "He helped me reach the top of the mountain," the self-proclaimed abominable showman said.

Michael Becker/FOX

Yeti's mail clue called the mythical creature a "true triple — nah — quadruple threat." "I'm excited you stepped up with a Masked Singer legend," the letter continued.

The furry white creature received Channing Tatum, Ne-Yo and Twista as guesses, but Cluedle-Doo told the panel they were "so far off." "He makes a much better panelist than you do," the disguised disruptor said.

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Chameleon closed out the quarterfinals with "Drop It Like It's Hot" by Snoop Dogg featuring Pharrell Williams. The color-changing lizard revealed in their clue package that they don't classify themselves as a singer, but they do have a theater background. "Even with a theater background, I never put on a show where I had to shake my tail," Chameleon said. "I'm used to just performing with my normal gear on." The reptile additionally identified Jackie Chan as their "personal hero."

Michael Becker/FOX

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Chameleon's letter identified them as a "friend of Martha Stewart" who played at Madison Square Garden, prompting predictions of NBA star Blake Griffin and rappers Snoop Dogg and Young Thug.

Then it came time for the panel and virtual audience to vote on their favorite performance of the night. Cannon, 40, admitted that the vote ended up being "one of the closest of the entire season," but that Russian Dolls ultimately received the least number of votes and would have to be unmasked.

Once the trio twisted off their doll heads, McCarthy, 48, and Scherzinger's guess of boy band Hanson turned out to be correct, making them the first group — and siblings — to compete together on the show.

Justin Lloyd / Newspix / Getty; Michael Becker/FOX. Hanson (L); The Russian Dolls on The Masked Singer

"You killed it because you probably had the most restricting costume," Scherzinger told the "MMMBop" singers. "But you've been here this long because your vocals slayed week after week."

"It's been a blast," Taylor Hanson, 38, said of the band's time on The Masked Singer.

Zac Hanson, 35, called the show "a unique opportunity to do something very different and also play to a whole new audience."

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Taylor added that the group appreciated the chance "to be able to just start with music and focus and say, 'Hey, you don't know what's behind this.'"

The Masked Singer airs Wednesdays (8 p.m.) on Fox.