SPOILER ALERT: Do not read ahead if you have not watched Season 7, Episode 5, of “The Masked Singer,” “Masking For a Duel — Round 2,” which aired April 6 on Fox.

That’s no illusion, it really was Vegas legends Penn and Teller unmasked on Wednesday night’s episode of “The Masked Singer.” Penn Jillette and his quiet partner Teller were disguised under the three-headed Hydra outfit. (Scroll down to watch the unmasking.)

And yes, that was Teller who did most of the singing — in two different voices, one as himself and one in an aristocratic-style voice patterned after Rex Harrison in “My Fair Lady.” (As a matter of fact, the duo dubbed the voice “Rex.”)

That may very well be the only time you’ll ever hear Teller — famously mute during all Penn & Teller appearances — actually talk. According to Jillette — who naturally spoke solo with Variety — the decision was made to have Teller sing most of the songs since Jillette’s booming voice is so recognizable.

“My voice is so damaged from years of being carny trash that I have just one voice,” Jillette said. “I have no ability to change my voice even slightly. I do sound like me and I do talk a lot, so our strategy was to have Teller do most of the singing, so that those voices, which nobody knows, would be the ones you concentrated on. We also picked songs that we figured wouldn’t pin our age.”

Why did the duo agree to participate in “The Masked Singer”? Quite frankly, “When someone calls up, we answer the phone, ‘Yes,’” Jillette said. “We are the longest running Las Vegas headliners in history. And we’re we’ve put about a quarter billion people into our theater here in the Penn & Teller theater. And we do that by people seeing us on TV. So we love doing all sorts of things on television, and we are not very picky.”

But “The Masked Singer” stood out, he added, because “this is so playful and so good natured and so sweet that it really wasn’t even an instant of hesitation to go on the show. I like the kindness of this show. So many of your competition shows seem to revel in some sort of unnecessary leanness, and this show is just happy.”

What was it like inside that costume? “It was fucking hell,” he said. “But Teller and I have spent our time hiding in little spaces with each other. We’ve been crammed behind mirrored cabinets and tiny miserable places our entire career! The tapping of the foot was excruciating to me. It’s the most elaborate suit they’ve ever done. We were just inches from falling down any second.”

Hydra was voted off after performing “Sharp Dressed Man,” by ZZ Top; the previous week, Penn and Teller sang “Hey Soul Sister,” by Train. This week’s “mega clue” pretty much gave away their identity: It was a deck of cards, a telling hint for the Vegas magicians. “How very curious, a deck of cards that’s all jokers!” Hydra said.

Had Hydra continued on “The Masked Singer,” Penn & Teller would have next performed “Karma Chameleon,” by Culture Club, Jillette added.

In the duel to determine who would be unmasked, Hydra and Armadillo faced off while performing “Walkin’ the Dog,” by Rufus Thomas (Armadillo) and “Two Princes,” by Spin Doctors (Hydra).

For Hydra, Guest panelist Nicole Byer got it right: Penn & Teller. Ken Jeong guessed “Lego Batman” Will Arnett and “Lego Joker” Zach Galiafianakis. Robin Thicke thought it was “South Park” creators Matt Stone and Trey Parker. Jenny McCarthy Wahlberg went with “Sesame Street’s” Bert and Ernie. Nicole Scherzinger went with Will Ferrell and John C. Riley.

(Other panel guesses earlier included Statler and Waldorf; “The Big Lebowski” Jeff Bridges/John Goodman/Steve Buscemi; “Three Amigos” Chevy Chase/Steve Martin/Martin Short; the Lonely Island guys; and Trey Parker and Matt Stone.)

Penn and Teller as Hydra joins the roster of unmasked celebrities that also includes Christie Brinkley as the Lemur , Jorge Garcia as Cyclops, Jordan Mailata as Thingamabob, Duff Goldman as McTerrier and Joe Buck as the Ram.

So far Firefly (“Team Good”) is set for the finale.

“The Masked Singer” entered Season 7 with 15 contestants, who have been divided into “The Good, the Bad and the Cuddly.” This season’s costumes include THE GOOD: Ringmaster, Armadillo, McTerrier, Firefly, Frog Prince; THE BAD: Hydra, Ram, Jack in the Box, Cyclops, Queen Cobra; THE CUDDLY: Baby Mammoth, Thingamabob, Lemur, Space Bunny, Miss Teddy.

The Season 7 contestants boast a combined 112 film appearances, 15 Grammy Nominations, eight Emmy Nominations, seven Super Bowl Performances, two Hollywood Walk of Fame Stars and two World Records.

In another change, the show’s panelists don’t appear to be competing for a “Golden Ear” trophy based on their first impressions of each masked performer (which McCarthy has won two times, but Scherzinger won last season) this season.

Here were the contestants and their performances on night five:

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Ringmaster, “The Masked Singer” Fox

Ringmaster (“Team Good”)

Song: “Super Bass,” by Nicki Minaj
Voiceover: “It was awesome to hear the crowd going wild for my first performance. Team Good is ready to take this all the way, and fool the panel every week.”
Mega clue: Guitar and guitar pick with “90s” written on it. “You should know that I’m a ‘90s chick, but I’ve been songwriting as long as I can remember.”
Panel guesses: Taylor Swift, Olivia Rodrigo, Alanis Morrissette, Zara Larson
Previous song: “The Climb,” by Miley Cyrus
Previous panel guesses: Olivia Rodrigo, Kacey Musgraves, Kelly Clarkson

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Armadillo, “The Masked Singer” Fox

Armadillo (“Team Good”)

Song: “I Fought the Law,” by the Bobby Fuller Four
Voiceover: “I will protect the Good with my life! That’s what I do for a living, I kick butt. I can’t wait for the next song because whatever comes my way, I was born ready!”
Mega clue: Keys and a motorcycle, while “Leader of the Pack” played. “So Nick, you’re the one who took my keys to the wild hog! It’s a shame these guys had to walk my bike out. Looks like it’s dead.”
Panel guesses: Gary Busey, Jay Leno, William H. Macy
Previous song: “Secret Agent Man,” by Johnny Rivers
Previous panel guesses: Chuck Norris, Erik Estrada, Vin Diesel

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Miss Teddy, “The Masked Singer” Fox

Miss Teddy (“Team Cuddly”)

Song: “Tell Me You Love Me,” by Demi Lovato
Voiceover: “I’m going to slow things down a little bit, get some feelings in there… My whole purpose of being here is to make people smile. I really do want America to have a hug because we’ve been through so much together. Some people will know my voice, some people won’t. But for me as an artist, no one’s going to expect me to be singing these songs.”
Mega clue: Grammy. “Winning a Grammy was one of the greatest moments of my career. For me, once I was afraid, I was petrified. Sometimes you have to go through life without anyone by your side. But you learn how to get along and you learn how to survive.”
Panel guesses: Gloria Gaynor, Jennifer Hudson, CeCe Winans
Previous song: “Tell It to My Heart,” by Taylor Dayne
Previous panel guesses: Lauryn Hill, Vanessa Williams, Jill Scott, CeCe Winans, CeCe Peniston, Loretta Devine

Watch the Hydra’s unmasking here: