Actually, though his looks seem to imply otherwise, G'Kar is a mammal.
(Costume designer Catherine Adair decided that the newborn Narns live in a
pouch in the father's body, and designed the costume with a slight suggestion
of that, a bit of a sling-look in the lower part.)

Don't ask, it wasn't my idea....

Re: G'Kar and Lyta, two things: 1) It's got nothing to do with romance,
strictly genetic business, and 2) what's not in the CFQ quote from the script
is the section where G'Kar mentions the need to alter the genetic structure to
make any offspring possible. "We still have to merge your genes with our
own," he says. Left alone, such mating is about as likely as a fish mating
with a bicycle to produce a walrus. But if the person(s) involved were
willing to go through *major* genetic restructuring, or be cloned and allow
*that* to be restructured, then it's possible, though still chancy at best.
Mixed species offspring are nearly unheard of in the B5 universe.

jms