Wow, it's been a long time since I posted a puzzle here... Sorry about that!
I asked a friend the other day what was his favourite film, but he'd reply only in riddles. I don't remember how he described the film as a whole, but about the first half he said:
I look small, but am vast.
A fireball, but in the past.
And about the second half:
In the air you barely see me.
You do me to get rid of me.
And about the middle:
A blue box from elsewhere,
But you, not I, go there.
What was the name of the film?
Note: you should be able to solve this without knowing anything about the film in question.