If you had a mouth ulcer it's because you've been telling lies.
A childhood belief about being ill

others believed things like this
- I used to think that the song "My Bonnie Lies Over the Ocean" was really "My Body Lies Over the Ocean."Anon
- When i was child i used to believe that if you tell lies your nose grows.Anon
- I used to believe rabbits could lay eggs. See what Easter is doing to our children? lies! lie I tell you!— Kitty Kat
- I used to believe if i told lies my nose grow like Pinnochio — Cindy
- I used to belive that if i put my foot in my mouth, I would get foot-and-mouth illness— Emily Sathrota
- i used to believe that if you farted out of your mouth, you'd die.— John Deere