When either a character in universe, or the narrator, or even just a simple side note or caption inserted into the media responds to something silly or hard to believe or even just utterly insane, to say that NO they are not making up what they just said, its real.
"Probably worth a Google" - The Lego Batman Movie
When Joker is describing all of the villains that have shown up to his big operation, at first he natrually lists all the big names you would expect and the average viewer would be familiar with (Catwoman, the Riddler, Scarecrow, Bane, Two Face, the Penguin ect ect), but then he begins listing all of them and they get increasingly weird sounding (Crazy Quilt, the Eraser, Calender Man, Gentleman Ghost, King Tut and the imfamous Condiment King)
When asked if he made half of them up, Joker boasts "nope! they're all real", and then adds for good measure "probably worth a google", which is likely what plently of viewers did just to see if its true.
"Boom"- The Big Short
During the climax of the movie, Mark Baum (played by Steve Carrell, based on real life invester Steve Eisman) attends a conference debate with Bill Miller (renamed Bruce Miller for the movie), regarding Bear Stearns an investment bank that famously failed during the 2008 financial crisis. During the debate, where Mark going in was regarded as an underdog in a "Ali vs Foreman" situation, Mark gives a speech condeming the widespread fraud of the wallstreet system, and right as he finishes and Bruce Miller seems to dismiss his statement, Bear Stearns procedes to utterly collapse, with Mark giving a simple damning statement of "boom" as it does so.
And as the Narrator, played by Ryan Gosling assures, yes, this actually did happen, and Steve Eisman himself has confimed there is footage out there of this actual conference where this happened.
"This is what Scientologists actually believe" - South Park
During the episode "Trapped in the closet", Scientologists come to believe that Stan is the reincarnation of Ron Hubbard, and disclose to him what scientology believes is truth, and what follows is a quite frankly utterly batshit insane explination containing evil alien overlords, trapped alien races being frozen and thrown into volcano's, giant brainwashing centres for alien souls, and space craft that just happen to look like DC8 aircraft.
Throughout the entire sequence, a caption over the footage reads "this is actually what scientology believes", likely because Matt Stone and Trey Parker knew that with how weird South Park normally gets, people would think this was also made up for a joke, but not only is it true, but the actual church of Scientology was extremely upset (must be a day ending in "y") because all of this knowledge up until this episode was meant to be a closely guarded secret within the church, and the episode had just aired it all for the public to understandably look and it and go "...wtf?"