Toy Guns = Police!
Police in the UK were called because somebody was wandering around brandishing firearms...and ended up besieging a cowboy-themed costume party. The party-goers have even warned the cops of their toy-gun affair, but that wasn't sufficient enough to prevent the police from checking out the partygoers for actual weapons. Luckily, nobody tried to fight back against the police with their plastic guns, or else the party would have ended very fast.