Don't let them fool you - they understand our language, even if they don't always agree with what we're saying.
For instance, "Get off the table!" is understood, although they may try to ignore you.
On Saturday, it was early and I was in the little room off my bedroom (OK, come on, you know where I was.) and I heard Caitlin singing in her room, down the hall. At my feet were both cats, lolling around. I called out to Caitlin and asked her if she'd go feed the cats in an ordinary voice. Nothing different than any other way I'd phrase something, no strange intonation, no hand gestures, just the simple request.
Both cats, even before she said "OK!", jumped up and went running for the stairs.
They may not like to hear "Stop that!", but they understand English perfectly fine.
So far my requests to "Go get Dad!" have been ignored. I suppose "Get me a snack!" is right out too, isn't it?