User blog comment:ArceusFan2013/January 9th - Another Avatar change!/@comment-24101104-20140109160120/@comment-6342425-20140109161822

1st has Mewtwo, 2nd has Suicune, 3rd has Groudon, 4th has Arceus.

Its the 4th generation Drex. As early as Diamond/Pearl and as late as X/Y.