James Corden thought his worst nightmare came true when Katie Couric completely wiped out during her April 1 appearance on The Late Late Show.

The normally poised journalist was standing atop a flight of stairs, waiting to walk onto stage when she fell all the way down them. Awkward. As expected, James was absolutely horrified, cursing as he ran over to make sure that Katie was okay.

Of course, it ended up being an epic April Fools' prank — and the woman who fell wasn't even Katie! She was a stunt double who successfully scared the pants off the newly minted talk show host.

"We've been talking about these stairs, we've been going back and forth going 'Are people going to ...?'" James said. "I was like, 'Oh, my god. Katie Couric's just died.'"

We can imagine how terrifying it would be to see someone as renowned as Katie Couric (or, you know, anyone in general) fall down your stairs in front of a live audience. Mad props to James for not bursting into tears, which would have been our reaction.

April Fools' pranks ran rampant during the annual day of mischief. Rihanna surprised Jimmy Kimmel by waking him up in the middle of the night, cranking her new single "Bitch Better Have My Money." Sam Smith raised eyebrows by controversially joking that he's actually straight. Amazon and Google got in on the fun on their respective sites, while John Green announced a fake novel. A radio morning show lamely faked an exclusive Zayn Malik interview. And, of course, the jury's still out on whether T-Pain's slip about Robert Pattinson and FKA Twigs being engaged is an April Fool's joke or actually true.

See Meryl Streep + More Stars Who Almost Died on Set