I had this happen on a flight recently. We were on the beverage cart in the middle of the airplane and someone in the vicinity of the exit rows let out an SBD. Never heard it coming, but the smell was so vile that I'm surprised the oxygen masks didn't deploy. It was at the end of a 14 hour day, and I was flying with one of my best friends. We were already slap happy from the long duty day, and this just about did us in. Both of us got a severe case of the giggles so badly that we couldn't make eye contact with each other without one of us almost losing composure. I finally excused myself from the cart and went to the galley to get my "laughs" out. I know you probably think it sounds very immature, but some times even grownups find "potty humor" as funny as our kids.
Here's a little vocabulary lesson for some of you. You know what f/a's call it when they have gas and walk through the cabin releasing it? Crop dusting.