OK.
Now, I don't consider previews, first appearances(like CGC). To me they are just advertisements. I hate seeing them in Registry Sets too. Would you say the original ads in Fallen Angel #22 or Cory Doctorow's Futuristic Tales of the Here and now: Craphound showing the Ghost Key and Keyhouse, their first appearances? Probably not. But, I have been hearing for the longest time how Doctor Who #1 was Locke & Key's first appearance. Considering it came out a week after Locke & Key #1, I wouldn't call it a preview or first appearance, myself. I also have been seeing on eBay, Speed Racer: Chronicles of the Racer #1 being billed as the 1st appearance too. But, that was the eleventh book(with too many variants) to have the preview in it, despite coming out(Feb.6th) before the February 20th release date of L&K #1. I have spent many months on the floors of regional LCS's researching what in fact was the true first preview. A preview that came out so fast, it had a spelling error in it(counselor).
The true first preview...
Corrected rather quickly...
So, I ask(Cheryl and Annaka excluded), what was the truly first "special" Locke & Key preview?