A sudden, extremely urgent need to defecate.
From "Whose Line is it Anyway" (Scenes From a Hat) 'Adults still experiencing the Terrible Two's'. : "Jim, I've made a decision about that promoti-- *GASP* Ooo!... *hobbles towards restroom*" (struck by the Terrible Two's mid-sentence).
No matter how old this kid is, they are always in their Terrible Two's when you have to babysit them.
Oh, you'll have to bear with Melanie - she's in her Terrible Two's.