In the sims 2 it is not as funny when a sim farts it is more where. they do it.
like on my guys mac and cheese or in another's face while there eating mac and cheese it is also vary vary gross and rude and yet funny of course I am a guy. but

if a stranger EVER farted in my face when I was eating anything I would ask them to leave even neat sims are to blame. farting is for the bathroom at a strangers house if at all I know it is a body function but maxis could have done better on the timing it is always or most of the time on another sims food or in another sims face and they just don't seem to care it would be funny to make a mod where if a sim farts in another sims face they get into a fight and the sim who farted gets a kick in the butt.

I've seen them do it a lot when they get up from eating at the table. Maybe it's programmed for after you eat.

And they think it's the funniest thing ever. Dude, your bodily functions are not that amusing.

Sloppy sims are more likely to fart and burp and such. Playful and/or grouchy sims might have something to do with it as well, but I'm not sure.

My sims hardly ever do it, because I mostly play with CAS sims, and I tend to give them 4-5 neat points so they'll act nice and clean up after themselves.

One time in a Downtown community lot, after enjoying his hamburger, my Sim got up and farted - right in front of Mrs. CrumpleBottom. :P

Daring lol. Did he get a beatdown?

I have seen highly neat sims fart as well. That's what drew my attention to it, because I was surprised.