First off—no, there is probably not an angry cat, or a snake, somewhere in your air conditioner. The latter could technically happen, but it’s extremely rare—and if it does happen it’s likely to be a small, harmless critter.
Anyway now that’s out of the way—what is causing that hissing noise coming from the direction of your air conditioner? Also described as a bubbling sound by some homeowners, it seems to resemble the sound a tire makes when air is escaping it.
This, dear homeowner, is likely refrigerant escaping your air conditioner. But what does that mean?