Since the old thread is dead and buried deep in the depths of the forum, let's create a new thread. It's the same basic premise: just post jokes about different characters based around things that they would never say.
To start us off.
Lancelot: Welcome back, Galahad.
Matthew: I'm not Galahad
Galahad (in Matthew's head): Technically, you kind of are.
Matthew: Shut up, Galahad.
Scathach: And you can all call me Auntie Scathach!
Shirou: You know, I once thought the vernacular was a sex organ.