Of course his friends all know this is just a terrible trick, and as he stands out of January's eye shot, he sticks out his tongue and wiggles it very suggestively, in true Stifler style. Then she begged for him to be her first, and Jim did all he could to turn her down. There's a memorable scene where Stifler stands beside January and asks one of his friends to take a picture of them. Walcott on the other hand, had no such notions. Her big nude scene was taking Stifler White into the billiards room. Then she has tequila poured over her breasts and licked off.
The Stifler Family ends up dominating the later films, but even then, Stifler is reimagined as more of a Jim, with those bumbling virgin qualities.
She showed a lot of cleavage and participated in some simulated action under the covers. That joke is really funny, and it's the type of humor the whole series has been based on. Bowden starred in American Reunionwhich seems to have spawned many future television stars. We have all wished we were Jim in that scene, and we have all pictured what we would have done differently to correct his mistake. She is the one that got the whole thing started.