Lulled into a false sense of security...
...the crew returns to sleep completely unaware that hidden in the new module a slavering alien - relieved and relaxed after a quick visit to the little xenomorph's room - is about to embark on 110 minutes of special-effects filled carnage and sexually suggestive egg laying until, in the dying scenes, it is (wo)mano-a-xeno with Astronaut Piper.
The dramatic final battle will play out like a ferocious arm wrestle until the xeno is knocked into a fiery re-entry by the standard issue NASA toolkit that Astronaut Piper cunningly put into elliptical orbit* at the beginning of the film. I mean mission.
Oh, and on the subject of suggested ablutionary device nomenclature "Number ones: Piss Taker", "Number twos: Moon Raker".
* deus ex machina+chekhov's gun!**
** http://en.wikipedia.org/wiki/Category:Plot_devices ***
*** http://en.wikipedia.org/wiki/Smart_arse , http://en.wikipedia.org/wiki/Sorry