Flatulence

Flatulence, also known as a fart, is the act of letting out gas from one's rear end, sometimes accompanied by a foul odor. Flatulence is considered rude to exhibit in public, and the person who lets out such should politely excuse himself afterward.

In mainstream Smurfs media and in the HERO: The Guardian Smurf story adaptation "Wonder The Naughty", Grouchy is the character to whom the habit of flatulence is attached, rather shamelessly in his case.