I'm trying to catch up with this, because I've been neglecting it...
Day 17: Favorite quote
"Sometimes the only sane answer to an insane world is insanity."
AND
"Mulder, it's me."
Day 18: Favorite mytharc or reoccurring storyline
Scully's abduction.
I most of the episodes that deal with that. Specially, 'Patient "X"' and 'The Red and the Black'.
I like how they came up with this arc because of GA's pregnancy (that was the reason, right?) and it was very succesful for the show, making it one of the key players of the whole story.
Sometimes I wonder what they would have done if the situation was different.
Day 19: Favorite prologue/epilogue
Well, I think the one for 'Trustno1' is really good and emotional. I haven't watched the episode yet, but I've seen the teaser and it brought tears to my eyes.
Click to view
I can't really remember any other right now, but the 'Bad Blood' one is kind of funny :P
Day 20: Favorite title for an episode
I could go with 'Folie a Deux' because it defines Mulder and Scully's relationship really well, but that one was chosen already.
I'm going to choose 'The Goldberg Variation' just because I love that theme and its variations.
Here's a video of Glenn Gould Playing the Goldberg Variations.
http://video.google.com/videoplay?docid=-6984208089899995423# I have this one as my ringtone, the part I've chosen begins at 1:51.
http://chirb.it/zL5Fvn