When Fred answered the phone for one potential customer, he opens with "You deserve a break today...". This was McDonald's slogan at the time (and again later in the early 80s, along with a slightly modified one in the mid 90s).
Fred's line when answering the phone--"Don't cook tonight, call Sanford Delight"--is a play on the jingle used by the fast-food restaurant chain Chicken Delight. In the 1960s the chain had over 1,000 locations in the U.S. and the jingle was widely advertised on radio.