Well let's hope she doesn't forget it
I can't even think of a song that she wouldn't do tbh. Every single song was an event. She was referred as the "California Gurls" singer, then the "Teenage Dream" singer, the "Firework" singer, the "E.T" singer ect.)
Queen of signature songs tbh. Even though TOTGA seems like the most forgettable hit, I think that song means a lot to her so she'll be performing it again, same with "Part Of Me".
If there's one song that was a single from the TD era that I wouldn't mind not being performed, I would go with "Last Friday Night" only because I dont think it means that much to her (lyrically)
I'd say "Firework" but that's her favorite song of hers so we'll be hearing it for years to come lol.
That performance was priceless!!
She will probably merge some. If she doesn't do Dressin Up, then that'll be her only released song she never performed. 
