the grills

I keep mine off.

I do have a Bernese Mountain Dog who chewed through my $5k Crystal Cable speaker cables...:)...and chewed up my Logitech 1000 universal remote... Still love her...

My cats used to use the exposed label edge of my stored records as a scratching post. The sleeves took a beating but the contents survived luckily.

I keep them off, but I can't hear a difference either way.

I like to leave my grills off, I find they use too much gas when kept on. It only takes a minute or two to warm up, not like the stereo which takes 15 or 30 minutes.
I do leave the grills on the speakers, can't say I notice a difference with or without.
Oh, and we have a big black and white cat

I checked my George Foreman manual and is says a hot dog takes five minutes but nothing about a yellow lab? Did you mean a black lab? I know of a good Cajun catfish recipe...