Write how much you enjoy the show, who your favorite character and your most favorite episode. That's usually what I do.

I'd suggest to write to them individually unless you know they send signed cast pictures.

Hi!
I was wondering how to write a letter to the cast of something? Like I` m trying to write to the cast of South Park and Family Guy, so how would I write to the whole cast of them? Im lost.
If I wanted to write to the whole cast of South Park, How would i write the letter??? :?
Thanks in advance,
{??} Daniela {??}