Trivia: The painting of Jeremy that Todd Cleary ('Keir O'Donnell') creates and gives to Jeremy was kept by Vaughn after filming.
Trivia: The "Lock It Up!" discussion in the movie was completely improvised by Vince Vaughn and Owen Wilson.
Trivia: John Beckwith's line, "I think we only use 10 per cent of our hearts", was ad-libbed by Owen Wilson.
Chosen answer: The substance is Visine Eye drops which is an old bartender trick for obnoxious drunks. Just a couple of drops in a drink will indeed make the person feel ill.
Damian Torres