You can put conforming clothing on characters it wasn't created for. Generally, it works best to scale and pose the clothing, rather than conform it. This won't work for animation, but is often good enough for stills.

There are also programs that let you actually convert the clothing to other figures. Wardrobe Wizard (www.philc.net) is the most popular.

Another possibility would be to turn the conforming clothing into dynamic cloth, and fit it to other characters that way. PhilC.net has a tutorial on how to turn conforming clothes into dynamic. And PoserFashion.net has a tutorial on how to fit dynamic clothing to other figures.