One character mentions "come home and start having kids," which implies making love.
There are lots of sex jokes throughout the entire movie.
The Godfather shrew, near the beginning of the scene, has a small imprint that can be seen in his crotch area. Later in the scene it is no longer present.
Two police hippos show off their naked fat bellies with drawings.
One of the lizards shows a bare foot in front of Nick and Judy, some shots are graphic.
Children won't notice it, but adults will likely notice various suggestive comments.
They pass through somewhere where a lot of animals are not wearing coverings for their lower parts, exposing them for a few visible seconds.
A goat who is getting a haicut gets her chest fur cut all around, leaving only fur for a bra.