So you’re a DM, GM, or whatever, and your players are dying to play a long-term Star Wars game. Or maybe they must, must, must trudge through the dangerous territory on the outskirts of Mordor as Frodo, Sam, and Gollum slink toward Mount Doom. Or perhaps they have to play a Buffy game because they totally love Giles. (And really, who doesn’t?) After a little while, I’m guessing that your players will want to show their mettle and screw with canonical characters or events. Maybe they want to shave Chewie or murder the Witch King of Angmar. Perhaps they want to send fake text messages from Xander to Spike so that evil Spike will murder pre-lesbian Willow. I dunno, people are weird.
My advice is—when it comes to messing with canon—withhold.
This advice is not born out of respect for the stories that already exist, though I do respect them a great deal. Well, not the new Star Wars movies, but the rest, sure. I respect the writers, the stories, and the influence they had on me—quite seriously. But that respect is not what drives my warning.
Instead, my prohibition is more practical. Once you’ve taken the ring from Elijah, water-boarded Palpatine, or replaced Buffy as the ultimate slayer, well, there’s every chance that your RPG group will lose interest. Sure you can create other problems—new Dark Lords, more magic items to rule them all, other rebellions—but it is my opinion that players are not likely to push forward once the stories they know and love have been upended. After that, there’s nothing but silliness to come. “My character takes over Middle Earth and opens a Wal-Mart in The Shire.” That may be fun for a week or two, but by then, Middle Earth will lose its luster.
In a universe with canon, I suggest, at best, barely meeting a recognized character, and that is all. Leave a sense of awe. Don’t wrinkle the famous story. I recall being a player in a long D&D campaign, and our DM mentioned that Merlin, The Merlin, may have visited the region we were about to enter. That fact alone kept us on our toes, and I then took the game more seriously. Had we met him, shaken hands, and given him a wedgie (or the appropriate combat equivalent), something would have been lost. I was psyched enough just to sense him in my character’s universe. We weren’t playing in a truly Arthurian setting, either—Merlin just happened to be there, rather like Ringo in The Beatles, and that was plenty.
So, if you want to play in an IP universe, as someone running the game, don’t bring in too many famous names. Maybe let your players catch a glimpse of Rhadaghast cataloguing Middle Earth bird migrations, but don’t let them sign up to join The Fellowship. If you want to adventure close to the canonized folk, run a game where your players sneak around The Fellowship to keep wargs at bay. Or maybe it is your players’ job to infiltrate a new vampire lair in San Diego, thus forcing the undead toward Buffy’s hometown. That way, the names are there, but the main line isn’t affected.
Hopefully I’ve made my point. Either way, I do want to reiterate that I’m not suggesting this path out of misplaced obligation to someone else’s printed (or filmed) tale. I am not one of those RPG blokes so overawed by canon that no person shall dare mess with it. If you tell me that in your game, your players walked right up to Gandalf and kicked his ass, thus helping Sauron lord over an age of terror unlike anything known since my awkward teenage years, I say, “As long as you had fun, cool!” If you want to kill Kinkaid before he meets Harry, I don’t care. Newsflash—the stories aren’t real. Even if the source setting is nonfictional—you want to play a Civil War game and murder Jefferson Davis before the secession—go for it. All I’m saying is that when the canon, whatever it may be, is severely disrupted, your players may miss the wonderful stories and characters that they already know so well.