90s kids’ TV favourite SM:TV Live was hosted by the trio on Saturday mornings between 1998 and 2001.
A one-off special reuniting the three piece called The Story of SM:TV Live first aired on TV on Boxing Day morning - Saturday, 26 December at 9:25AM on ITV.
Alternatively, it will then be repeated in prime time on Sunday, 27 December at 8PM on ITV.
ITV reveal: "This celebration show will feature brand new interviews with Ant & Dec and Cat in a recreation of the SM:TV set which takes them back inside the same studio they used to broadcast from every Saturday morning.
"Covering the first three years of the show (1999-2001) - which catapulted the three friends and hosts to stardom - they reminisce on how the show came to be, how it evolved, what made it a success, their favourite segments and how it made them the presenters they are today
"Delving back through the archives, all the SM:TV favourites will be covered including Challenge Ant, Wonky Donkey, the Postbag dance, Pokemon Rap, Dec’s crush on Sabrina the Teenage Witch and of course, Chums."
The show will also feature interviews with regular SM:TV guests and celebrity fans who reminisce on their memories on growing up with the show when they were kids and what made it so special.
Guests confirmed to appear include Kylie Minogue, Stephen Mulhern, Fleur East and Scarlett Moffatt.
The Story of SM:TV Live premiered on Saturday, 26 December at 9:25AM on ITV.
The special forms part of Ant and Dec's celebration of 30 years on TV, which also involves the launch of their new book.
"Ant and Dec hold a special place in the hearts of TV viewers everywhere. This is their epic story, with never-before-seen photography and the very best tales from their 30 years in TV," a teaser reads.
SMTV began on 29th August 1998 and ran for five years, although Ant and Dec left the show in 2001, followed by Cat in 2002.