User blog comment:RyuKirin/Fairy Tail Manga's 27th Volume to Bundle 2nd Anime DVD/@comment-1839664-20110217230750

I did, and it said that they will be "animating the omake that was published on the Sorcerer Magazine that was bundled with the volume 16 special edition, Fairy Academy Yankee-Kun and Yankee-Chan." The story portion, when translated, talks about a transfer student named Lucy and her meeting with the delinquent Natsu, Gray, the Class Representative Erza. It went on further with Erza and Lucy shopping when they meet the students from Phantom Academy.

Oh, also, the crossover of the two series is actually published on volume 11 of "Yankee-Kun and Megane-Chan", and has never been published on Fairy Tail series at all.