Mark Rober searches for good samaritans as the guest host of ‘Jimmy Kimmel Live’

Mark Rober is an engineer, YouTube star, and marine conservationist. As of July 14, he’s also a late-night TV host.

Rober, who has over 22 million subscribers on his YouTube channel, stepped in for Jimmy Kimmel to guest host an episode of the comedian’s namesake ABC show. In addition to giving Kimmel a night off, Rober also used his Jimmy Kimmel Live! appearance to promote The Revengineers, an upcoming Discovery Channel show produced by Kimmel.

“Thank you for clapping,” Rober said after being introduced as the Jimmy Kimmel Live! guest host, “even though most of you have no clue who I am.” By the end of the episode, any viewers who were unfamiliar with Rober got a pretty good idea of what the creator’s channel is all about. Segments included a musical experiment with Demi Lovato and a toothpaste-based prank. Rober also alluded to The Revengineers when introducing a man-on-the-street segment he filmed, in which the Jimmy Kimmel Live! team set up ridiculous requests for aid in hopes of convincing good samaritans to stop and help.

There may have been some Jimmy Kimmel Live! audience members who didn’t know Rober, but the show’s normal host is definitely familiar with the prankish engineer who filled in for him. Rober has helped Kimmel execute April Fools’ Day jokes in recent years, and the two personalities also teamed up for a star-studded live stream that raised money for Next For Autism.

And Rober is hardly the only YouTube star with a connection to Jimmy Kimmel. The late-night host is the co-founder of the entertainment company Wheelhouse, which has been aggressively expanding into the digital media space since launching its DNA division last year.

Kimmel’s decision to tap Rober as a guest host shows the faith he has in the former NASA employee, and Rober knocked his late-night gig out of the park. He could definitely carry his own show in the future, but he’ll need to get through The Revengineers first. The Discovery Channel show does not yet have an official release date.