Party-animal Rick Gassko (Tom Hanks), who makes his living as a school bus driver, decides to finally settle down and marry his girlfriend Debbie Thompson (Tawny Kitaen). After gathering his buddies to give them the news, his shocked friends (led by Adrian Zmed) decide to throw him the bachelor party to end all bachelor parties. The bride's wealthy, conservative parents are not at all happy with her decision and her father decides to enlist the help of Debbie's ex-boyfriend Cole Whittier (Robert Prescott) to break them up and win her back.
While Debbie worries and goes off to her bridal shower thrown by her friends, Rick heads off to the bachelor party and promises to remain faithful. Both parties start off on the wrong foot thanks to a little sabotage by Cole. As the bachelor party starts to heat up, Debbie and the girls decide to get even with Rick and his friends by having a party of their own. Both parties eventually collide leading to Debbie accusing Rick of infidelity.
Both parties end up becoming one big drunken orgy and the bachelors' hotel room ends up getting trashed much to the chagrin of the hotel's ever-frustrated manager (Kenneth Kimmins). Adding to the confusion is Rick's friend, Brad who has become despondent over his wife breaking up with him. At various points during the movie, he riotously botches every suicide he attempts. He even tries slitting his wrists with an electric razor to which Rick says, "Well.....at least your wrists will be smooth and kissable."
Rick convinces Debbie of his love and faithfulness just as the party is raided by the police. In the ensuing melee, Rick and Debbie become separated and Cole kidnaps Debbie leaving Rick and his friends to chase after them culminating in a showdown between Rick and Cole, which includes a chase through a 36-screen movie theater. Rick and Cole have a humorous fist fight just below the movie screen which is showing a 3D movie. The fight is in direct synchronization to the on-screen fist fight. A female audience member gets punched in the face but attributes it to a 3D movie effect. Rick wins and he and Debbie embrace. After the wedding, Rick and Debbie are driven to the airport for their honeymoon in Rick's school bus driven by a laughing Brad.

Question: To what did a theater watcher mistakenly attribute being punched to?
Answer: The ongoing film's 3D effect.
Alternative answer: The 3D movie effects.