Sex

Sex is an intimate interpersonal activity among humans and various species of animals that is used for procreation, pleasure, and expressing love for one another. In mainstream Smurfs media, it is a topic that is generally avoided due to the characters and their stories being created mostly for children, and any mention of Smurfs engaging in this activity would most likely appear in "non-canonical" works of an adult nature. However, it can be assumed that the Smurfs do have some level of education on this topic when it comes to how humans and animals reproduce, since the Smurfs themselves can only reproduce through non-physical means.

Empath: The Luckiest Smurf stories
In the EMPATH: The Luckiest Smurf story series, the Smurfs do engage in this form of activity, though it mostly occurs with married couples, since Smurf culture emphasizes marital fidelity and the creation of families as virtues. However, the only known case of this activity happening out of wedlock was when Aristotle fathered Lillithina's second son Brainy to replace the assumed loss of her first son Empath after her separation from her husband Culliford. Whether there were any societal repricussions when this was made public knowledge, if it was even made known at all, is unknown.