Taking a risk when farting?

I just ate fast food, now I have to fart like crazy, and this is bad. One thing i've been always scared about, is poop coming out with a fart. So many times over my life I thought that may have happend after an intense fart, but I don't think it ever did. Does this happen to people? and how easily? How intense does a fart have to be for poop to come out with it?... whoa, i have to check this one now... jeeze