Which TV series would you like Avril to make a guest appearance in?
Think about whether she is relevant to the series/ could play a valid part.
What kind of character would she play?
What sort of situation could she be involved in?
I'd personally love to see her make an appearance in How I Met Your Mother. She could quite easily play a good role in that as herself as one of the celebrities that the group regularly seem to be meeting/chasing around New York.
It would be funny to watch her response to Barney as well (although I'm not sure where his character is going after last season's finale)