Mandel "hated" his last appearance on Ellen's show, where he almost lost consciousness.
Moments after the "America's Got Talent" judge sat down for his interview, Ellen jumped straight to the point: "Last time you were here, we almost killed you."
The audience laughed, but Mandel assured everyone "that's not even a joke. I swear to you, this is not a funny story. I thought I was gonna die"
The comedian explained he would appear on Ellen's show "anytime you call" and agreed to appear back in February to play a game called "The Masked Dancer." Admitting he "didn't do any research" before coming on, he had no idea what he was walking into when he arrived on set.
"I showed up here and it's your take on 'The Masked Singer,'" he explained, referring to the competition show where celebrities perform with masks on, as judges try and guess their identities. "They said, 'You'll wear a mask and you'll dance."
Mandel was immediately put off by the game when someone backstage put his freaky pug mask on him, as the self-described "germaphobe" noticed a weird smell inside. As the show's producers counted him down to his stage entrance, he recalled going, "I can't breathe, somebody I can't breathe" before hearing Cardi B music.
"I'm starting to get dizzy and I feel like I'm losing consciousness. I said, I can't pass out, so maybe if I just lay down and continue to dance," he explained, as footage from his previous appearance played on the screen behind him. "Then you didn't rush questions. I'm almost dying and then I open the mouth and I got some air, but I almost died."
"Those aren't good masks," he scolded DeGeneres. "It's an air tight, I almost died. That's me acting like I'm having a good time. I hated it and I'm just glad to be back with oxygen!"
Watch Mandel's dangerous dance from earlier this year in full below: