(Strip Number 931, Original Publication Date, 3 September 1985)
Panel 1: Elly tells Never-had-a-friend-in-his-life John that he can't possibly know what Connie meant to her.
Panel 2: She then explains that a BFF is someone very dear with whom one can share intimate secrets.
Panel 3: She then sighs and says that she told her everything.
Panel 4: Panicky Idiot John squeals "EVERYTHING?!?!" as if he has secrets worth keeping.
Summary: We're meant to believe that John is worried because there's knowledge about him that might destroy his reputation. I should think that given the potty fracas, he's worrying about a lasting humiliation that's already taken place.