Ant McPartlin and Declan Donnelly joked that boss Simon Cowell was "atrocious" to work with as he often forgot or didn't bother to learn his lines during filming.
The duo were on on the set of filming their spoof drama Men in Brown for Saturday Night Takeaway when they spoke about boss Simon's acting talents.
Ant and Dec were filming a celebrity masked ball, which saw them go hunting for a celebrity who was actually an alien with 'squids'. They have to find the dodgy celeb before they manage to unleash hell.
Among the celebs with cameos in the spoof includes Simon Cowell, Paddy McGuinness, Hugh Bonneville, Richard Ayoade, Amanda Holden and Amber Gill.
Ant joked: "They're lining up to... no they're not, we've pleaded with them to be here."
The pair were then asked whether any celebrities had surprised them with their acting and they revealed Simon had.
Ant explained: "We've worked with him for years and he's not one for learning lines or remembering line, but he turned up today - he's like a different man!"
"Keep it between us, but normally he's atrocious at delivering lines," Dec quipped.
Ant added: "But today he was brilliant!"
"He's absolutely brilliant, I don't know what's happened," Dec replied. "I think he's been taking acting lessons. He must have!"
He added cheekily: "Maybe that's how he's lost loads of weight - he's got the squids!"
*Ant and Dec's Saturday Night Takeaway returns tomorrow at 7pm on ITV
