@robmandu – actually, it asked it in several ways.
Unfortunately, the explanation I liked best is no longer there. I’d say Marvin asked the question when talking to the mattress:
<Marvin> Think of a number, any number.
<Mattress> Ehm, five?
<Marvin> WRONG!
I like to think “Think of a number, any number” is the ultimate question to life, the universe and everything, even if it doesn’t have a question mark ;-)