How about:
Marlo from Simon and Simon
Maximillion from The Bionic Woman
Meatball from Black Sheep Squadron
Mignon from Green Acres
Muffett from Mork and Mindy
Ralph from The Flip Wilson Show
Ranger from M A S H
Ranger from The Waltons
Rowlf from The Jimmy Dean Show
Mr Magoos dog McBarker
McGruff The Crime Dog
Neil from The Topper Show
Oh and lets not forget Marmaduke! Love Marmaduke