The "man in a schoolgirl outfit with hairy legs" Christie sees in Book 1 becomes a Brick Joke in Book 2, when Bethany sees the exact same thing. Christie, at this point a con veteran, tells her it could've been worse. Beth asks how, and Christie responds that he "could've dropped his heart-shaped wand and bent over to pick it up." Cue the sound of Beth's brain cracking in two.
From Book 2: Monica demands to know if Beth uses magic fairy pixie dust on her art to make it so good, and if so, where can she get some?
And Beth's response, "Magic fairy pixie dust? Um, no..."
A Funny Background Event from Book 3. On page 121, amid the many faceless con goers, one of them has got on a wig with curly ringlets... and visible chin stubble.