Happy belated birthday Casualty!
Casualty looks sort of odd in the Bahamut universe. But I suppose it's only logical that he turns out different than the rest if you drew him over from a real picture. I think you made him look quite nice though, he looks better than your other character models in my opinion. Perhaps you should've considered doing the same for all your other characters, although the sudden change might be a bit weird and they could be harder to animate.
Anyway this happy birthday flash isn't much special, but I wasn't expecting anything great from it. Technically it was well made and as usual the voice-acting was done pretty well.
Overall 7 out of 10, 3 out of 5.
~Auz