Melon is a highly controversial aspect of the game, as mentioning the word causes Trip to immediately eject the player from the house, causing a bad ending.
Trip is usually tolerant, as minor insults like telling him to shut up, or saying obscenities cause him to attempt to laugh it off saying "Ha, never afraid to push our buttons, ha ha ha, heh...", or may cause Grace to intervene by saying "that was just a little poke in the ribs between friends". Only when Trip becomes angry will he eject the player from the house.
The word melon is a slang term to refer to the female breasts, and could be interpreted as an obscenity, as mentioning other slang terms causes a similar reaction from Trip.