You drank coffee earlier and now you need to get to the bathroom before the show starts.
Walk up the stairs on the right and there will be a guard asking for your ticket. Left of the door is a pink poster. Use the poster to read instructions on how to get your ticket. So, use the MODS billboard in the middle and then use the poster left of the door again to see that a ticket drops on the floor.
Pickup the TICKET and although it is still visible on the floor, it is in your inventory. Take the ticket from your inventory and give it to the guard (15/10). The guard will move and you can walk further to the right. Use the left door of the two toilet rooms. It has the caption MEN above it. You can now see the show in peace.
Game source: A copy of the game was found here on the internet.