Katy Perry mocks Sesame Street' ban with low-cut Elmo top

'Ur So Gay' singer Katy Perry has made a mockery of her Sesame Street ban by wearing a low-cut Elmo top during an appearance on Saturday Night Live.

Perry, 25, who was originally scheduled just to sing two tracks, wanted to take part in a comedy skit to mark the controversy created by her appearance on the children's show.

The singer appeared as a busty 16-year-old librarian on mock women's daytime talk show 'Bronx Beat'.

"What the hell happened to your shirt? Looks like today's show was brought by the number 38 and the letters double-D!" The Sun quoted one of the hosts as asking her.

Perry looked down and cupped her breasts.

"I guess I developed over the summer," she said.

The singer hams up the part, chewing gum wildly, playing with her hair and pulling wild facial gestures while putting on a teenage voice.

"You do your thing at the library - the kids come for the boobies and stay for the books. Everybody wins," the host added.