For those not in the know; Charlico Agathorne (Yes, that was her given name but they never used it in either canon) Cupid was supposed to be bridging gap between Monster High and Ever After High.
Problem was, she wasn't quite an established character in the MH-verse. She debuted in
Why Do Ghouls Fall in Love, got one doll that would go on to be ridiculously expensive, was maybe in two Monster High webisodes (I clearly remember one with her, Frankie, and Abbey and a school project about the
weather, seriously, is this high school or not), and pushed to a brand that most parents thought was a knock-off of MH anyway.
I know there was build up to a legitimate crossover movie - you can find storyboards on youtube - but there really should have been some establishing special, with clear, established characters visiting EAH and then leaving Cupid over there. The teaser website (I distinctly remember 'Village of Book End' being one domain that lead to the site; They seem to have been taken down in every capacity) was beautiful and atmospheric, and involved Frankie, Clawdeen, and Draculaura expressing good wishes to Cupid in her new adventure.
Cupid was never a character I cared too deeply about, though I did like both outfits she wore.