I remember that line after every episode of Cheers that I used to watch, however I think that it followed all shows by UBU productions that Gary David Goldberg, the producer of UBU Productions, Inc. founded in 1981. I think that the dog's name was actually "UBU", and after the "sit" comment followed an encouraging "Good Dog!" comment and then a quick, single dog bark. Ubu Roi (who died in 1984), had played Frisbee with Goldberg during his college days. I hope this helps :) Good luck!