I usually say "you stay mister....I'll be back later....you be a good boy." Then I say "Be good boys...take care of eachother" (for both my dog and 2 cats). Then when I go to my car, I look up to the second floor (my apartment is on the second floor) and he is on the couch looking at me through a pane in the window. He looks like he is saying "hey, where are you going?" and "you forgot me". He looks soooooo sad. I always wave goodbye.