Mine are that
- I used to think JubyPhonic was a really realistic Vocaloid
- I used to think Gumi was not a Vocaloid (I'm a fail, I know)
- I used to think Sakine Meiko and MEIKO were the same
- ^ with KAITO and Shion Kaito
- I used UTAU horribly wrong
- I did once think Miku was the first Vocaloid
- I used to think UTAUs were just more robotic Vocaloids
- And many more... (of which I can't think of right now xc)