I'd also like to add: you're still auditioning for a job, an amazingly awesome job, but still a job. There will be people who are looking at you who pretty high up on the Universal Entertainment ladder. Don't act unprofessional or dress like you just woke up. I personally will show up in jeans and probably a shirt & tie. There're some people who will come in shorts and a nice t-shirt, which I find still totally acceptable given the job requirements.
oh, and please take a shower before you show up.