Meta: At what point am I violating copyright/trademark laws?

[Phantasm]

Here's the deal.  In the upcoming Silver Arrow #7, the title
character's parents are visiting him in the hospital.  Because they're
trying to protect his identity, they show up wearing Halloween
costumes from a few years ago.

In my mind, those costumes are mockups of the ones worn by Michael
Keaton and Michelle Pfeiffer in _Batman Returns_. (At least the Bat-
suit won't have nipples! WTF, Schumacher?!)  So when asked for their
names by the nurse on duty at the ICU, they reply "Bruce Wayne" and
"Selena Kyle Wayne".  The nurse's reaction is probably going to be
something like "... you're kidding, right?", clearly not believing the
names.

Now, I know I've used "What would Batman do?" as a plot point in the
past, referencing the old Adam West deathtraps.  But in this case, am
I possibly violating DC's copyrights/trademarks by doing this, or am I
still covered under "fair use", as I'm making it quite clear that the
characters are only dressed up as such?

Your thoughts on this are appreciated.