Ah Gen 3. Contrary to others when they write EX era in upper case I instincitively assume Gen 5-6 over 3rd’s originals having lower case ex’es, a case of spending lots of studying on Bulbapedia haha.
Similar to the random placed Jirachi, Absol and Charmander line to some degree (plus being some of Mitsuhiro Arita’s best. Period.) is one of many wondrous gems from that gen which you find uncovering when you trek through each set. 
I got that same reaction upon learning about such nicety cards secret for being secret (Dark Raichu, this) when compared to a ritualistic alternative which is what made them special to me. Haven’t seen such similar commodity until the recent Tag All Stars Eevee GX.