Legislators have received letters from dogs ("Archie" sent a Christmas card to Sen. Robert Dole's new canine pet), letters on 2 x 4s (80 were once sent by Michigan lumbermen protesting unrestricted imports of Canadian timber), letters from certifiable loonies ("Dear Senator . . . As a man of integrity, could you please write my wife Nancy informing her that the U.S. government deliberately poisoned me . . .") and hosts of others that provide comic relief to beleaguered staffers.

But not all the prize congressional letters come from constituents. Intentionally and unintentionally, plenty of doozies have been sent out from the other side.

As bloopers, few can match the unfortunate classic dispatched a few years ago by one eastern congressman. It was sent to a constituent, bitter about his mother's mugging death in D.C. and the court's handling of the case. "Dear -----," read the reply: "We were so sorry to hear about your sick cow. Enclosed is a booklet from the U.S. Department of Agriculture . . ."

How to explain such a monumental blunder? You can always blame it on the computer. "Sometimes," the congressional source of the story offers weakly, "it's a product of uncontrolled technology. The staffers who put out the mail are issue folks, not computer people."

Other celebrated replies are right on target.

Dole has a favorite response for standouts in the stable of kooks and cranks attached to his -- like every other -- congressional office. (Some legislative aides keep records on such regular correspondents in file boxes labeled STUN: nuts spelled backwards.) "I thought you should know," writes Dole, "that somebody has been sending ridiculous letters to me and using your name."

Sen. Alfonse D'Amato (R-N.Y.) got wise recently to a letter-writer posing as a 9-year-old saddled with the same distinctive first name. "Dear Alfonse," he wrote back to the 53-year-old pretender, "I got your nice letter and want you to know I sympathize with your problem. But it's not your biggest problem. Your biggest problem is that if I ever get a hold of you, I'll break your neck."

But the champion of tart congressional correspondence was probably the late Sen. Stephen Young (D-Ohio), called -- in polite understatement -- the most "liberated" letter-writer to hit Washington since Harry Truman.

Writing with uncustomary disregard for winning reelection, he told off one constituent: "Don't give me any more of your unsolicited advice. I know it costs nothing -- but that's exactly what it's worth."

When Wayde Newkirk of Alliance, Ohio, proposed he be tarred and feathered, Young wrote back: "Buster, when you try to tar and feather me . . . be sure to have four or five strong men as helpers else I will knock your false teeth down into your gullet, you lowdown skunk."

To John R. Lee of Cleveland, who argued the United States should reduce North Vietnam to a nuclear wasteland, he replied: "Buster, you are a necrophiliac jerk . . . In your insulting letter, you make reference to something beyond your comprehension. It is evident your comprehension is very low grade . . . In addition, you are the north end of a horse going south."

There was compensation, however, for targets of Young's literary onslaughts. When he addressed them as "liars," they knew, at least, they weren't getting a form letter.