No, the killer joke is just German-sounding nonsense.
I can, however give you what the script says :
from The Complete Monty Python’s Flying Circus : All the Words, vol. 1, ep. 1
If you really must know, an entirely literal translation would be :
[when] is the now-piece [good] and ‘Slotermeyer’?
Yes! … at-hither dog /[Bavarian dog?] the Oder (river)/[or?] the Flipper-[forest] [hurried].
Words in brackets indicate the sort of word possibly intended since it was spoken, since they’re misspelled as German words. Slotermeyer has no meaning, but could be mistaken for a surname (spelled Slotermeier, though). Also ‘sputen’ (hurry) is a rare verb that I had to hunt for, and anyway ‘gersput’ isn’t a correct form.
Unfortunately the ‘dirty Hungarian phrase-book’ is in vol. 2, but I expect it’s similar nonsense.