Surprise Party is a guessing game. An audience member is chosen to host a party and is promptly taken out of listening range. Five "guests" are then chosen. Each guest is then endowed by the audience with some odd quirk or physical deformity (example: has three legs, is cheese-a-phobic, honks whenever verbs are spoken).
The host then returns and, one by one, the guests arrive. It is the task of the host to guess the quirk of each guest. The guests must act out their personal quirk, but are forbidden from directly mentioning what it is. This rule holds for any part of the quirk (i.e., a guest with three legs cannot say, "Look! I'm wearing three shoes!") When the host correctly guesses the quirk of the guest, that guest leaves the party and the next guest enters.
The only special rules are: 1) If the host guesses part of the quirk, then the guest can directly mention that part (i.e. Host - "You have three feet?" (this to the three-legged guest) Reply - "No, but I have three of something below the waist.") 2) If the host is having a particularly hard time guessing the quirk, another guest can enter the party to help give clues. The game ends when the host has correctly guessed all the quirks.