My dad keeps farting in the buiscuit tin?

this is a silly story but its true, im 13 and my dad has this disgusting habbit of farting into the buiscuit tin and its so annoying and when my friends come round he offers them a buiscuit then watches them eating it while hes laughing, my friends always ask - why does your dad always laugh when were eating our buiscuit ,iv made up that many excuses i cant think of any moe plz help