Would you believe that owl is the squab of the Underneath? It'd be a lie, but it sounds like it could be true, and if you say it with enough confidence, and bring enough salt and pepper with you...
In one of Lucien's pockets - unfortunately, his pants pockets - he has some sticks of owl jerky. That's probably what the ratter is snuffling. This thing might have teeth like sawblades, but the strips are hard as boot leather. It might still buy some time.
It's a shame, really. Anything short of doing that to the meat wouldn't be enough to disinfect- wait.
As he holds the strips out over the creature's weasel-nose; "Ailee, I think they think you're a rat. Would you please, without making any sudden movements, grab the flask from my shirt and souse yourself in it? This rude little thing doesn't like the smell of you, so it might be better to smell like something else for a bit."
Then, louder, to the bartender; "This is all going to come across as a good joke I'm sure, but if you can't bring him to heel before he starts biting, the Archmage might have to ruin it for everyone. So let's call it now, while we can all still laugh about it?"
It seems too slow to get pedantic on the difference between a mouse and a rat, if they'd care about that anyway. Let's speak softly and carry a big stick instead, if Ailee's already gone to all the trouble of showing off.
EDIT Wait. If these are catfish, and the tails have scales, does that mean they hate... ratfish?