This is the one moment in the series where Ash let go of a Pokemon for a good reason. Butterfree wanted to cross the ocean with his mate and Ash was kind and respectful enough to let him do so. I find this to be far more of a touching episode than a tragic one.
Nurse Joy: We hope to see you again! (Translation: We hope you get the crap beaten out of you so that you require medical treatment again!) Not so nice in a different light, is it?
I don't use "uber" Pokemon, I don't calculate stat values, I don't use cheating devices, I don't breed my way to perfection, and I don't care about natures. I catch my Pokemon the way they are, and treat them like individuals instead of brainless drones. If you use this philosophy, copy & paste this into your signature. (Started by Tyranitar)