The prank occurred during a discussion of the UK premiere of The Lost City, a new adventure film starring Channing Tatum and Sandra Bullock.
After sharing clips from the premiere, presenter Vick Hope teased that a celebrity guest would be appearing live in the studio: Tatum himself.
Garraway was seen looking shocked and delighted at the news, before her co-star informed her that it was in fact just a seasonal prank, at which point her expression turned to one of disappointment.
Elsewhere during Friday’s episode (1 April), presenter Laura Tobin was seen interviewing a man about a rare and priceless potted plant, only to accidentally smash the plant on the floor.
The guest was then seen storming off set, although GMB viewers cottoned on quickly to the idea that this was all too likely another April Fool’s prank.
“This is bloody hilarious, although I suspect its an April Fool prank,” wrote one person.
“A very silly April fool with Laura Tobin, I bet everyone knew that was going to happen,” wrote another.
Later in the episode, Tobin confirmed to viewers that it was in fact a prank.
Good Morning Britain airs weekdays from 6am on ITV.