Frequent but mild sexual jokes and references, mostly involving Shel the turtle. Most will go over younger audiences heads but some are a bit more overt
One character is constantly pining for a wild animal of a related species who is also attracted to her, she makes several references to how "sexy" he is and how he wants to "ravage" her and has several fantasies with him in it, though none actually show anything one sees him doing a sort of pole dance.
A male dog character frequently humps inanimate objects when he gets excited. One episode has him take medication which gives him a visible but censored erection as a side effect for the entire episode, which other characters comment on. It is played for laughs only.
A cat character gives birth to kittens, we later see in a flashback this character asking a male if he wants to do that "thing" they do, though the actual act is not seen. The character is oblivious and doesn't understand this as the cause of the kittens being born.