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A sequel, prequel, or any other addition to a series which just doesn't belong. Created solely to squeeze every last cent out of a successful franchise, and often made by someone other than the original creator.
Sam: Remember the Terminator movies, from when we were kids? Those were the days.

Greg: Remember them? They're still making 'em!

Sam: Nope, I'm pretty sure they're not. All that's left now are tack-ons.
by Inertient November 23, 2009
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