Some fans believed the star was Panic! At The Disco frontman, Brendon Urie, with viewers commenting on the eccentric costume.
Urie is known for his quirky stage costumes, and occasionally embracing high heels during performances, so fans took the costume to be a major clue.
One fan said on Twitter: “I think @brendonurie is the Leopard in #maskedsinger, plus he hasn’t streamed in a while, and hasn’t Tweeted.”
Fans took his social media silence to be a clue, with many other viewers jumping on the theory he could be behind the Leopard.
However, other viewers claimed the singer did not sound like Urie at all, and they have thrown other names into the ring.