Some game elements are easier to drift than others, and White Wolf’s preludes fall into that category. They’re mechanics-free, so there’s no conversion work, and the underlying concept — as well as the end results — are excellent.
For those who’ve never played a WW game (Vampire: The Masquerade, Mage: The Awakening, etc.), a prelude is a brief solo session that you run for each player.
It takes place before the campaign begins, and is used to flesh out the character, lay the groundwork for the game, test out the PC’s abilities and give your player a chance to see what playing their character is like.
Like most solo gaming, preludes are intimate in ways that group play is not — it’s an interesting experience, and one that’s quite enjoyable as a player. (See Two to Tango: GMing a Solo Campaign for more about solo games.)
Most GMs I’ve gamed with allow players to tweak their characters after a prelude, which works quite well. You can also mix it up a bit and run a prelude for more than one player at a time, although I wouldn’t recommend going past two — at that point, you’re pretty much just running a regular session.
Offhand, I can’t think of any RPGs where this wouldn’t be beneficial, but there might be some exceptions out there. Have you drifted the prelude concept into other games? How did it go? Do you tweak WW’s basic formula in any way?