Mouth Fart?

So Kid#3 is walking out of the restaurant that we frequent and he proclaims " I just farted in my mouth" WHAT?  I asked my husband if he heard what Kid #3 just said and he said no so I repeated it.  My husband thought that I was mistaken and to prove him wrong Kid #3 proclaimed it again with a little giggle of satisfaction.  So apparently our new family mission statement is to say excuse me when we fart in our mouths.