I saw this sign while riding the moving walkway going into the Venentian from the strip. I took a quick picture to share. It looks like you get free admission to Madame Tussauds Wax Attraction when you purchase tickets to the Blue Man Group.
I am not 100% sure if tickets have to be purchased there or can be purchased anywhere and then simply show a ticket stub. I will try to get this verified, but the sign in the pic looks like you might have to purchase the Blue Man tickets at that location.
If you are wondering, Madame Tussauds is located off the moving walkway closest to the Casino Royale/Harrahs area of the strip.