Square Enix made a tower defense spinoff with the Final Fantasy Tactics Advance characters called Crystal Defenders. Now, those Hume Soldiers and Seeq Beserkers are charging into Puzzle & Dragons from GungHo Online Entertainment. You can add Crystal Defenders characters to your Puzzle & Dragons party and fight Tonberrys in a crystal dungeon. Apparently, there are enemy crystals too.
GungHo Online Entertainment also made a weird moogle dragon and if you give it magic stones you can get Crystal Defenders characters. The collaboration kicks off now, but it looks like it’s just for Japan. Puzzle & Dragons is available in English on iOS.