Poynter, Ellie Taylor and Lawson's Ryan Fletcher take part in a spoof of The Great British Bake Off, with the McFly star discovering a human bottom in his mixing bowl.
Asked before the challenge how he would react to a 'soggy bottom', Poynter said: "I'm not afraid of the arse."
The trio were then advised to add flour and other baking ingredients to their bowls in front of the panellists.
Mutya Buena and Mae Martin are also guests on next week's show (Thursday, March 6).
Fake Reaction continues tonight (February 27) at 10pm on ITV2, with guests Rylan Clark, Natalie Anderson, Matt Richardson and Josie Gibson.