Cole Temperton, 21, made his big-screen debut after his actress mother, who played a holiday rep, recommended him to the film's director.
"My mum plays a holiday rep in the film and she said a few extras had turned down the role,' Temperton explained to The Sun.
"I told her I'd be up for it and a day later she had a word with directors. I got a call asking me to email over a picture of myself... showing everything."
Buckley revealed to Digital Spy upon the movie's release that he simply "wasn't up for" appearing naked.
Temperton, who was paid £300 for the part, added: "It wasn't about the money, it's about doing something not many other people can say they've done.
"My girlfriend went to see it with their family and told them afterwards which part I played. They found it quite funny."
> The Inbetweeners movie holds UK box office No.1 spot
Watch Digital Spy's recent interview with The Inbetweeners stars Simon Bird, Joe Thomas, Blake Harrison and James Buckley below: