[SaveFerris]

“Is it safe?” is also used in another film, a comedy.

NOW I understand where it came from.

[ctdonath2]

[Another loud roar]

ZAPHOD:
It’s a carbon copy of the Ravenous Bugblatter Beast of Traal - or I’m a Vogon’s Grandmother!

ARTHUR:
The Ravenous Bugblatter Beast of Traal! Is it safe?

[Sound of the Ravenous Bugblatter Beast of Traal salivating]

FORD:
Oh Yes! It’s perfectly safe - it’s just us who are in trouble. If that’s the admiral and he still wants his coffee it ain’t sponge fingers he’s gonna dunk in it.

- The Hitchhikers Guide to the Galaxy

[Larry Lucido]

This scene is also a reference to Marathon Man.