Well, there are a different versions of retcons. Retcons can mean....
1.) Two or three different story elements from past issues are revealed by a current creative team to have been really linked together. For instance, the reveal that Wanda/Scarlet Witch and Pietro/Quicksilver were Magneto's children didn't come until they were Avengers, after they had left Magneto's Brotherhood of Evil. Basically they put together some early X-Men and Avengers threads to come up that background reveal.
2.) That a new story element reveals or adds to a previous story element. For instance, in a mid 80s comic "Wolverine versus Spiderman" (I think that was the title) 2 part miniseries it was revealed that MJ had always known that Peter was Spiderman, even before he told her, because she was visiting her aunt next door the night Uncle Ben died and saw Peter return to the house afterwards, taking off his costume. That didn't change the previous story, but added to it, adding shades of meaning to previous MJ and Peter interactions.
3.) A previous story element is written over by deliberate creative team attempt. This is Crisis on Infinite Earths, Superboy's punch and now the Spiderman magic handwaving.
These three definitions of retcons, and stetcons, all come fron Peter David's Comic Scriptwriting book.
Finally finished the Anya for Buffy 8.10:
Buffy: If this is a European beach, why is my top still tied?
Daniel Craig: Buffy, you know not to listen to your critics, but you should
especially
never listen to your fans.
Willow: Wait, what?
Buffy: Uh, hang on. I might have got the scripts mixed up. I'm a little distracted, what with the
thousand feet of empty air
beneath us.
Willow: But it's great! We're up on high, defying gravity.
Buffy: Yeah, that's sorta the problem.
Willow: Aw, you and Angel should talk about acrophobia some time. Anyway, I'll take us lower.
Buffy: Oh, thank AAAAAAAAHH NO POWERDIVES!
Xander: Dawn, by my amazing powers of talking-other-people-into-doing-stuff, I present you - fresh clothes.
Dawn: OMG Xander!! You are the best not-a-big-brother ever! Gimmee Gimmee Gimmee!
Xander: Whoa, little lady; this thing's loaded you knommmmmmff!!
Willow: And then there's hot cocoa, and snuggles, and skiing, and why is she wearing my top from the cover of issue #3?
Buffy: That's cool. And your actual girlfriend?
Willow: ...I think you're missing the point of the game, Buff.
Buffy: Never mind. Are we there?
Willow: Yep. Thank you for flying Willow Air, please make sure your lesbian is in an upright and locked....Y'know what? I don't really wanna finish that joke.
Buffy: So. We're in a generically bucolic setting, with a run-down hose with a girl outside.
Willow: Well, the house is probably the Pit of Doom inside, and the girl is here to make sure reality doesn't go all kerflooey.
Buffy: Pretty standard setup, then.
Robin: Welcome to Mount Doom. Tourists to the left, petitioners to the right.
Buffy: Bzuh?
Willow: She experiences reality differently than normal, thanks to the whole "minder" thing.
Robin: Good luck rescuing the Prince of Roses.
Buffy: ....ooookay. Why would anybody join up for a job like that?
Willow: She didn't join up. She was chosen by impassive cosmic forces to perform a vital task that she can never really rest from.
Buffy: I get the feeling there's something pointy here, but I'm too distracted by this symbolically endless stair to follow up.
Willow: The wit of the staircase always comes too late.
Xander: We will now have a brief intermission while I panic
yet again
about my masculinity, with bonus exposition.
Buffy: Can we take a break from fantasizing to talk about your girlfriend? Actually, can we just have a giant monster attack before I dig this hole any deeper?
TV 2 Demonic 4 TV: CUSTOMER SATISFACTION GUARANTEED!
Buffy: Thanks! Also, ow. Anyway we're here about-
TV2D4TV: Merchandising! Sales pitches!
Fray
tie-ins!
Buffy: Well, for example. Can you help us?
TV2D4TV: Please! I can remember it for you
wholesale.
Willow: So the secret behind the Slayer army is grand larceny?
Buffy: Hey, it's not
my
fault all those secret Watcher bank accounts turned out to be fanon!
Willow: Buff, you know how people get when you ill-get their ill-gotten gains.
Buffy: All I did was liberate some sparklies no one was using. What about you and your Hot Lesbian Demonic Sex?
Xander: Y'know Dawn, having fallen for a bad-boy with a smooth line doesn't really make it as a deep, dark secret. Nonetheless, I will now gloat that it was me you opened your big, big heart to.
Robin: If the chick does not crack the shell of the the egg, it will die unborn.
Willow: What? Wait, is this a sneak preview?
Robin: We're in reruns. This is the part where someone you love and trust betrays you.
Kennedy: Mememe! Memememe, mememememe! Tara?
Willow: Y'know, the downside to getting over feeling guilty about the reasons your lover died that weren't your fault, is it frees you up to feel guilty about the reasons that
actually were.
TV2D4TV: Well, now I know all your secrets, so I'm gonna tell all my demonic friendslist, nyah, nyah, nyah.
Willow: COMBO....
Buffy: BREAKER!
TV2D4TV: (Fatality)
Shack: BZZORCH!
Robin: Modenkainen's Sphere (continued...)
( continues...) of Kerflooey Containage!
Willow: Wow! Ow. Hey, sorry about the blowing-up-your-job thing...
Robin: Yay, paid vacation! So where are you guys off to?
Buffy: Anywhere but here.
