I used to believe that the dog on Sesame Street was real. Can you imagine- a 6 foot tall dog? Not only that, but I even asked for one for Xmas.
A childhood belief about cats and dogs

others believed things like this
- I used to believe that “Emo” was related to Elmo from Sesame Street.Anon
- I seriously used to believe that Bert from Sesame Street lived in my closet and that he was going to kill me.— Liz
- I thought that Count Dracula was the count from Sesame StreetAnon
- I used to believe cartoons where real people. You can imagine how that went... — Emma
- The Whit house down the street was the real "White House". — SG
- I used to belive that if i put my foot in my mouth, I would get foot-and-mouth illness— Emily Sathrota