Actually, I would say "Something Rotten" had TWO clever ad campaigns. The first involved the cartoons of various characters and the second was the one about inviting people to see a Tony loser. I thought they were both brilliant (as was the show, IMO).
Regarding The Phantom of the Opera, I'm staring at my wall, which is full of various posters. The mask and rose are great, although the rose comes and goes. (The rose image does not actually have much to do with the original show, but they're linked in the audience members' minds). The Phantom poster (I don't know if it's an ad) with a mask and background made up of hundreds of small phantom scenes and masks, like a Seurat painting, is brilliant. The touring ones, with a red background, instead of black or blue, and gold lettering are just blah, in my view. However, the one that does not qualify as sensible or attractive at all is the 20th anniversary poster:
https://www.musicmotion.com/Broadway-Posters/phantom-of-the-opera-poster.asp
Audrey, the Phantom Phanatic, who nonetheless would rather be Jean Valjean, who knew how to make lemonade out of lemons.