In HG/SS when the policeman asked what the trainer who had stolen the Pokemon's name was, I thought that if I put in the wrong answer something bad would happen, so I spent ages trying to remember what it said on his Trainer card (which didn't even tell you -.-) then I looked it up on the net and found out that you just made up his name. Oh.
And yeah, I only ever trained my starter in my first ever game, Sapphire. Thought my Blaziken was invincible. Bad idea.
Oh, and I evolved a Magikarp into Gyrados on one of my games, never replaced Splash because I thought that it was exactly the same as the Waterfall HM and would let me go up waterfalls or whatever, because of the Pokedex entry. When I tried to get up the waterfall I was so disappointed, and then I thought it might work if I didn't evolve the Magikarp, so I caught another one and tried again. What was I thinking?