Poison thing here as well. My poor Cindaquil got poisoned coming back to Cherrygrove after receiving the Pokemon Egg. My screen started flashing, and I actually called my Dad over. After he came over, the little textbox popped up that said, "CINDAQUIL fainted..." Then I said, "Oh... nevermind..."
I also didn't understand the concept of stairs inside buildings (this was only the second video game I played. My first was more of a 3D platform adventure game), and I spent five minutes or so going up and down the stairs in my house wondering, "Why does the screen keep changing and flashing when I go over to this tile?" Pfft.