Despite rumors, he was never a sniper, nor was he ever in the military, nor did he wear the sweaters to cover up his tattoos. Nobody is quite sure just where the rumors started.
For some reason, Mister Rogers is famous for saying, "Can you say ____?" The line appears in several parodies but he literally never said it on the show, and in fact thought the phrase would be an insult to the intelligence of even his very young audience.
He did ask his viewers "Can you _____ now?" at least once, though.
The Danza: Quite a few. Bob Trow as Robert Troll and Bob Dog, Joe Negri as Handyman Negri, Don Brockett as Chef Brockett, Audrey Roth as Audrey Paulifficate, Maggie Stewart as Mayor Maggie....
Also, Bill Nye, whose television debut was actually on this show before he got his own.
Nice Character, Mean Actor: Completely and utterly averted. Despite whatever fake stories flitter around the internet and other presenters of children's shows, Mr Rogers took pride in being every bit as warm and friendly in real life as he was on television.
One of Us: Fred said that each of the characters in the neighborhood of make believe had a little aspect of his own personality. We all know if he had Lady Elaine Fairchild in him, he was truly a normal human like the rest of us.
What Could Have Been: When Sesame Street's Big Bird appeared on the show, Rogers' original script called for his performer, Caroll Spinney, to remove his costume and discuss the inner-workings of the Big Bird puppet. Spinney objected, however, because he didn't believe in ruining the illusion of Big Bird for the children, having been advised not to by Jim Henson. Big Bird ended up appearing as himself in the Neighborhood of Make-Believe.
As a compromise, the same episode had Rogers donning a giraffe costume and telling the viewers, "When you see big make-believe creatures in parades or in plays or on television, you can know that the people inside are just pretending to be something else."