Here's some of them.

There will be a grey cat with yellow eyes holding a drawing in it's mouth and upon interacting with it, Jack says, "Aw, how c00t, it's thinks it's people! It says Vic on the collar."

There will be a box with eyes in the Flipside, and upon interacting with it, Dave will say, "STEVE".

There's a sentient fishbowl that will say "sesbian lex" when interacting with it.

Sometimes, there will be weird uncanny versions of the normal enemies in the Flipside, and upon the first time encountering them, Dave will say, "looks like it's some sort of f a l s e a n i m a t r o n i c"

There may be some more added throughout development