There are a few crude references sprinkled throughout the movie that are brief in nature and not dwelled upon.

Shrek is seen comedically naked "stripping" on a metal chain. Buttocks are seen but full frontal nudity is defused.

Skimpy outfits are worn by some characters.

One song talks about "getting head" from a chick.

Two uses of the word "f**k" (one use is partially obscured and the other use is not). Other milder terms like "ass", "hell", "slut", and "damn" are used infrequently.