It was when Rex did the thing with the contact lenses...

Oh. Wait. You're talking about the other series, aren't you.

In that case, I'm not sure there was a clever moment, though there was a fairly fun romp that demonstrates the usual problems with time travel at all. (She's named for herself? Gimme a break.) I got the impression that someone was shooting for satire that cleverly blended into seriousness. I'm not sure they quite got to that point, but at least the initial satire was there.