Jon Sheen recalls his first impression (sort of) of Derek thusly:

Those who know me have heard this frequently enough to be sick of it. Those
who don't, won't care.

Nevertheless.

I met Derek when I came to work at UltraNet, We'd been co-workers in the
very same very small department for about a week before clapping eyes on one
another* when our first mutual in-the-office shift fell on a saturday.

We were sizing one another up, chatting about almost nothing, far from
having found any mutual interests, science-fiction or otherwise, when another
employee asked if the Cadillac in the parking lot was, in fact, mine. 

Derek, puzzling that a mere, poverty-stricken support rep like himself could
afford a Cadillac, looked impressed, and I hastened to allay any notion that
I had two ha'pennies to rub together. 

"It's a piece of crap," I said, "but I like it anyway, because it looks like
it was built by the Centauri." At which point I burst into my famous
semi-lame Londo Mollari persona, and said "Now, now it's just a
six-hundred-dollar car, but in the grand old days of the Great Centauri
Republic, there were _fleets_ of cars! The roads _glittered_ with
them... "

The joys of Breaking Derek -- neither of us having even mentioned B5 yet at
that point -- were suddenly clear to me.

--
*Not strictly true. I later remembered seeing him several months before
being hired at a previous interview for an UltraNet position. I went in
feeling a little nervous because I'm not just big, by gum, I'm fat, and
that can sometimes make people weird about hiring you. I glimpsed Derek
sitting at a desk as I was being led through the not-large tech support
office, and suddenly thought, "Okay, I'm cool!"