When the members of Lambda Lambda Lambda are watching Harold Skolnick remotely controlling the robot to mess with the Alpha Beta's pimple cream, Harold Skolnick narrates "We're here at the world renowned Tri-Lamb fraternity bathroom where we've secretly replaced their Pimple Clear with pimple inducing ingredients". He should have said they were at the Alpha Beta fraternity's bathroom. It was mentioned earlier in the film that the Tri-Lamb house and everything in it had been given to the Alpha Betas, however, so Alpha Betas using the Tri-Lamb bathroom is not an error.