There was a girl that woke up and everyoe had vanished, she ended up going to the mall and changing. That's all I can remember.

Also there was another movie where a girl woke up and she had a penis. After that should could not decide if she wanted to be a boy or a girl so she played the role of a boy to see if she liked it.

For the first one are you talking about Night Of The Comet (http://www.imdb.com/title/tt0087799/)?

Not even going to attempt the second one.

Willy/Milly (http://www.imdb.com/title/tt0092216/) for the second movie.