Though I'm a fan of it's history today, when I was 5, I got the wrong idea of Professor Burp's Bubbleworks (thinking it was themed around an evil scientist), which meant I was one terrified lad for the whole ride, and wouldnt return to it until the ducks invaded!
Well, to be honest, I didnt mind first going on it, until I saw the Prof animatronic suddenly drop it's head to one side! (back then I REALLY wasn't a big fan of animatronics!)