I read on TV Tropes Mr. Rogers really said "Can you say (enter noun here)?" only once, but then stopped because he didn't believe in talking down to his child audience.
I used to watch the show sometimes when my parents got cable and we had access to PBS. Many fans who grew up watching found the show soothing and relaxing, but good ol' Fred Rogers would sometimes talk about scary and taboo stuff like nuclear war or divorce, and in the Land of Make Believe there was a puppet named Lady Elaine Fairchilde, who the closet to a villain on the show, although she wasn't really evil. She looked a stereotypical witch without the pointy hat, with a long nose with a wart on it and both her nose and cheeks were bright red as if she was really drunk.
I'll take Mr. Dressup any day. And he used to be on Mr. Roger's.