We never thought we'd see this sports star transform into a sea slug.

Leaf Sheep—which just so happens to be Thurston Cartea real and very adorable aquatic animal—was revealed to be a NFL legend during The Masked Singer's season 12 premiere.

Fellow footballer DeMarcus Ware, who competed as Koala on the Fox singing competition show's 11th season, introduced Leaf Sheep during the Sept. 25 episode by calling the anonymous celebrity the G.O.A.T.—a.k.a. the greatest of all time. But when it came for Leaf Sheep to tease his real identity, the retired athlete couldn't help but address his extremely unusual undersea costume first and foremost.

"I know, you're very confused right now," he told fans in a video package. "And so was I until about three days ago. But the leaf sheep is a real thing. Look it up."

Plus, the star noted his costume is actually fitting now that he's no longer on quarterback duties.

"Now these days, I'm a little sluggish, but you should have seen me in my prime," he continued. "I made a total splash, scored headlines, topped the country's charts, even revived a franchise. Now, I'm here to keep the good times rolling."

Leaf Sheep's pre-package video included clues like a quarter—which judge Robin Thicke immediately clocked as a quarterback reference—and a seahorse wearing a cowboy hat.

However, Leaf Sheep's cover of Tim McGraw's "I Like It, I Love It" landed him in the bottom and he was sent home first.

As for the judges' guesses, Robin guessed Dallas Cowboys alum Troy Aikman while Jenny McCarthy picked Tom Brady and Rita Ora guessed Billy Bob Thornton. But Ken Jeong was the only one to correctly choose former Denver Broncos quarterback John Elway.

"It was definitely not my comfort zone doing this," the 64-year-old shared after his elimination, "but I’m in retirement now. I had the opportunity and took advantage of it."

In fact, the NFL star did it all for the next generation.

"I had a great time," he added. "I think all the grandkids are gonna be happy to see Pappy jump out of the Leaf Sheep."

Keep reading to meet the other mystery celebs who are going on to compete next week. The Masked Singer airs Wednesdays at 8 p.m. on Fox.

Leaf Sheep (which happens to be an actual sea animal) was revealed to be NFL Hall of Fame legend John Elway, who was sent home first.

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