During a play trough of Half life 2, I noticed Barney mentions something about a cat he "still has nightmares about". Alyx then starts to ask a few times, without answer, what cat he refers to. It is mentioned as Barney and Kleiner debate how safe the teleportation device has become from the last time it was used.
I never got to play Half life 1, so I am curious if this is either a reference to a HL1 scene, or if it's just a random gag left for us to ponder about. I don't mind spoilers, as you get key hints trough HL2 as to what happened during HL1 anyway.
So, if it actually is a thing and not just some random gag, what cat does Barney refer to during his talk with Kleiner?