Disclaimer: in real life, the roommate who shares my bathroom is perfectly considerate and does not monopolize it this way. But I was looking for a tune to parody and sometimes the muse makes weird leaps. On that note, this is sung to the tune of "Take Me Out to the Ballgame."
Please come out of the bathroom
You’ve exhausted your turn
You’ve got to share it with us, you know
You’re not the only one who’s got to go
So it’s time for you to come out now
Don’t make me break down the door
Because you’ve been hiding in there
Half an hour or more!