don't stay too long (especially if in an f class lav) as if there is a fam on board, dollars to hockey pucks says he'll be the next person standing in line "waiting to use the lav" after you leave. had it happen to me when i had a major case of "praying to ralph" as dinner from the night before decided not to agree with me at 35,000 feet. sure enough, one of the 2 was waiting in line and spent an awfully long time in the lav after i left. he briefly spoke with the f/a upon exiting, gave aher a smile and kept giving me the "occasional look" throughout the remainder of the flight.