Ordinarily, you could say GET BROWN CAT or GET GREY CAT and Adventuron knows exactly which object you're talking about from the object ids brown_cat and grey_cat. If you just say GET CAT and only one is present, it knows to get that one. If you say GET CAT and both cats are present it prompts you for clarification and you have to enter 1 or 2. (Personally, I hate this mechanism, but that's just the way it is.)
Because of the two-word restriction in this jam, you must be able to do everything with two words (verb + noun), so you can't use three-word inputs (verb + adjective + noun). However, you can be a little more creative. I have a similar situation and the way I'm handling this is if you say GET CAT, it says "Which one?" You can then say GET BROWN or GET GREY. This is easily implemented with some clever match statements and appropriate tests.
In my case, the objects requiring disambiguation are in the same location. It gets a little more complicated if they can move around. In this case, you can say GET CAT and if there's only one cat present, then you get it. If there's two or more cats present, then you do what I described above.