(This is taken from the current update of this infrequently updated page of mine about movie translations which probably no one reads, so I'm putting it here, too.)
Of course, I practically had to make up many new words and grammar for Borat to use (with lots of help from Tomas Baldynsky).
The joke at the dinner with the confusion about "retired" / "retard" cannot be translated and had to be replaced with something similar. After trying out several things, we settled on "emmental" / "mental". I.e. "I worked in construction, I am now retired" had to be changed to "I import cheeses, eidam, emmental..."
We changed the name of of Borat's son from "Huey Lewis" (who is almost unknown over here) to "Kessel Buntes" (the popular Communist Germany entertainment show was called "Ein Kessel Buntes").
"I am like the movie star, Dirty Harold. Go ahead, make my day, Jew." - This famous Dirty Harry line is totally unknown over here, mainly because it was translated differently in different releases of the movie (and not always correctly). In Czech, Borat says "I am like the movie star, Schwarz Nigger. Hasta la pizda, Jew" (where "pizda" is slang for "vagina"). Coincidentally, I originally thought "pizda" is much less vulgar (I only knew it as meaning "ugly woman") and was surprised when Disney dubbing supervisor didn't let me use it in "Cars". :)
Finally, one of the most baffling episodes in my translation career: I wanted to accurately translate the faux "Kazakhstan Anthem" at the end of the movie. However, the dialogue list didn't contain its text and only said "for translation, use the text in the rodeo scene" - which I couldn't do because the anthem in the rodeo scene is much shorter than the one at the end of the movie. I sent several e-mails to Fox and even asked at IMDB.com boards. No answer. Then I tried to translate the whole anthem just by ear. After I've done that, Fox issued a memo to all foreign distributors saying that "The anthem at the end MUST NOT BE TRANSLATED" and my translation had to be removed. Bizarre...