Weird R-rating
The plot and comedy points to a family friendly G-rated movie
Yet there is an explicit nude scene and a lot of profanity. Odd
You also have to remember this was still a year prior to the PG-13 rating being introduced. Which is probably would've been if it existed (and what the other vacation movies were rated). So it was either PG or R.
shareI think it still would have gotten an R because there is too much profanity. You can only say the F-bomb once, and it has to be a non-sexual F-bomb, in a PG-13 movie and I think it's said nine times (three times at once). The MPAA's rating system is very autistic.
Nudity wasn't much of an issue in the 80's, though. The sequel had lots of tits and was PG-13.