Just ran into a weird room on the first floor. Can't find info via Google

[Sparrow]

It was a graveyard. with a few rows of tombstones. It had one bulletkin in it and he was wearing a red and yellow hat. Killed him...nothing happened..moved on.

Did I miss some kind of special opportunity?

[Alphanumerai]

Thankfully not, it's just a nice little set-piece, the only place those Cardinal bulletkin spawn before their native floor.