I was scavenging in the frozen Imago gallery, melting things - as you will when you're scavenging, and I melted a pile of ice to discover another Bioshock cat.
This one was upright, not tipped over. Like a living cat would be, except he's frozen. I moved my reticle to see if any word would come up for this kitty.
And laughed. I found Schrodinger the cat!
He's an Easter egg I'd heard about and forgotten, so I was very pleased to have stumbled upon him. (Being frozen, he is both alive and dead at the same time = Schrodinger's cat.)
If the upcoming Bioshock Infinite doesn't have this cat in it, I shall be highly disappointed.