HI Anna,
I just started working for Virgin Blue about four months ago and really really enjoy my job.
Yes it is true that you can be asked to make up a jingle or put on a little skit-- but I assure you that this isn't to see how silly you can be. The recruitment team are looking to see how you work and interact with the others in your group.
I have sent you an email, so feel free to ask me any other questions you may have!!
love SMILE