The only time you would see Caster in regular clothing is right here in this OVA series, that spans 4 short clips portraying the cast of Type Moon’s well-known visual novels (notably that of Fate/Stay Night and Tsukihime). A little more about it after the jump.
It’s a parody of the characters in a parallel world, keeping their personalities (mostly) intact while being thrown into game shows and pair them with other characters in situations that would seem completely out of place in the main story.
Brutally speaking, it’s just pure fan-service. Oh, but there are no shower scenes and the like, this is purely for the hilarity of seeing the characters in a different setting. So if you go into it thinking you’re in for another crazy plot you’d be mistaken.
For fans of the series though, you’d likely find it as enjoyable as I did. Newcomers should stay away though, as it’ll probably be boredom spelt in full for them. In a nutshell, take the holy grail war out of Fate/Stay Night, take the “hunting” out of Tsukihime and leave the harem, and you’ll get Carnival Phantasm.
I’m looking forward to the 2nd set of OVAs already. (Oh, and you DO get to vote on whether they should pick their “default” to go out with, or to go for the harem ending.) 😀