What is it about three-day holidays and TV marathons? Yesterday Hallmark offered a full day of The Mary Tyler Moore Show, and today it's filling its daytime schedule with episodes of The Bob Newhart Show. But of all the marathons you could be watching today, this one — or, perhaps the mini-M*A*S*H-athon from 2 p.m. to 9 p.m. ET on TV Land — is definitely the most worthy.