Bob Hoskins in "Who Framed Roger Rabbit" was talking to a cartoon
that was supposed to be a cartoon; we were never expected to accept it as
a real, live breathing creature. We're so far doing one more major CGI
critter as an alien for year two, but the rendering power required is
absolutely MASSIVE. (I'd also note that the budget for "Rabbit" was a LOT
more than an average B5 episode.)

The problem, always, is having the alien interact with humans, not
vice-versa. You have two choices: a human in prosthetics, or essentially
a puppet/animatronic face. And the overall technology still isn't here
yet to do that convincingly, up close, for television. And if you want
any real *emotion* from the character, you're going to have to have an
actor inside.

jms