Back around the mid-1980s to 1990s, I read a novel of the future when man was traveling the stars. The main character of the novel was a crewman aboard a starship. Other characters on board the ship included a sharp tongued engineer, the Captain of the starship and his XO. In one line I recall the Engineer referring to the Captain and his XO as"Tubby And Fop". The Crewman meets what he thinks to be another crewman only to discover that she is an Alien insect that in her true form appears as an over sized Praying Mantis. The Mantis convinces the crewman to assist her in getting her to the correct Parallel Universe. There is a hitch however. He has to help her get through another Universe, where the Germans won the Second World War, first.
This sounds a bit like The Battle for Terra Two by Stephen Ames Berry. If so, the quote you remember is actually Fatty and Fop:
Engineer N'Trol requests permission to lower the shield for periodic maintenance," reported K'Raoda, Implaca-ble's third officer.
D'Trelna sighed. "What did N'Trol actually say, T'Lei?"
"He said, sir, 'Tell Fatty and the fop to let me fix the number eight shield generator, or we'll be eating meteors next watch.'
The alien is a chap called Fwolkes not a girl though:
Rippling, the Fwolkes-form shimmered away, replaced by six feet of mantislike insect, erect on four of its six limbs, its two upper limbs ending in gently undulating tentacles. Bulbous red eyes shifted between the two men before it melted back into the brigadier.
It's so long since I read the book I can't remember the details, but I'm fairly certain that in the parallel Earth the Germans won the war and set up a Fourth Reich. America exists as the only opposition to the German empire.