Melissa McCarthy and Jennifer Aniston Hilariously Debate Global Warming While Filling in for Jimmy Kimmel

Melissa McCarthy at 2017 Emmys

The actresses go head-to-head debating science during 'Jimmy Kimmel Live.'

Melissa McCarthy and Jennifer Aniston are feuding over science!

While filling in as a guest host for Jimmy Kimmel -- who's out following his son's most recent heart surgery -- on Jimmy Kimmel Live! on Thursday, the comedian hilariously debated with Aniston over whether gravity is real or just a hoax, mocking the issue of global warming.

"As you know, there has been a lot of talk these days about the environment, our changing climate and global warming. As some people say, it's real. And then the really smart people, they know it's a rouse, invented by the Illuminati," jokes McCarthy, who was dressed as a giant menorah. "But there is an even bigger issue facing our planet, one that has gone undebunked for hundreds of years."

The clip then flashes to a video of "famous person Melissa McCarthy" who explains, "There's a subject the mainstream media doesn't want you to hear about."

"They say we shouldn't ask questions. They say it’s 'settled science,'" she continues. "They call people who disagree with them 'duh-nye-urz.' Of course, I'm talking about gravity."

She continues on, saying the "so-called Theory of Gravitivity was conceived by Isaac Newton."

"Every day, school children are brainwashed into believing they cannot fly," she says.

That's when "less famous person" Jennifer Aniston joins in, counteracting McCarthy's claims. "Melissa, what are you talking about?" she asks. "People can't fly." 

"Who told you that gravity is real?" McCarthy said in response, to which Aniston replied, “Pretty much every scientist in the world told me that."

Watch the full video below:

McCarthy is among one of the many celebrities who is filling in for Kimmel while his 8-month-old son, Billy, recovers from heart surgery.

During his guest appearance, Neil Patrick Harris updated the audience that Billy is "recovering well" and is "eating" and "smiling."

Hear the latest update in the video below.