Like Ash regretted trading his Butterfree for Raticate; have you ever traded a Pokémon and then wished you hadn't? Did you even ask to trade back?
Way back in Generation II, my best friend at the time and I were playing through Silver and Crystal, respectively, for the first time.
I had become tremendously attached to my team from day one. However, I felt that my Ariados (the first wild Pokémon I caught in Crystal, as a Spinarak) wasn't cutting it 6 badges in, he kept getting defeated.
I traded Ariados to my friend in exchange for his Donphan and off he went.
A few days later (I'm almost embarrassed to admit this) I found myself missing my Ariados. Donphan is a great Pokémon, and fitted into my team well; but he wasn't my Ariados.
I went over to his house and asked to trade back. He said no at first, but luckily the promise of a stronger Donphan returning to his team changed his mind.
tl;dr I missed my Ariados when I traded him away because I am a pussy. :P
Has anything similar happened to you? Please share!