Halloween III: Season of the Witch
Original Star: Jamie Lee Curtis
Replacement: Stacey Nelkin
Reason For the Switch: In order to get Halloween creator John Carpenter to agree to oversee a third film, the producers had to agree that the next chapter would not revolve around Curtis' Laurie Strode or her pursuer The Shape a.k.a. Michael Myers. So writer/director Tommy Lee Wallace hit upon the idea of a costume company that hatches a plot to hide something deadly in kids' Halloween masks. Nelkin plays the heroine that discovers their scheme and attempts to put a stop to it.
Did It Work?: Let's just say that there's a reason why Myers was promptly resurrected for the fourth Halloween...

The Next Karate Kid
Original Star: Ralph Macchio
Replacement: Hilary Swank
Reason For the Switch: Age mostly. Since Macchio was 28 when he made the third movie, it was pretty silly to keep calling him "kid."
Did It Work?: Sadly, The Next Karate Kid missed the girl-power wave of action movies by a few years and Swank's Julie Pierce vanished into obscurity. (That the movie kinda sucked didn't help matters.) It took remaking the first film virtually beat-for-beat with Jaden Smith and Jackie Chan in the lead roles to get The Karate Kid kicking again.

Home Alone 3
Original Star: Macaulay Culkin
Replacement: Alex D. Linz
Reason For the Switch: Culkin's career was washed up by 1994, only four short years after the first Home Alone, so producers turned to 8-year-old Linz to carry on the franchise as a new resourceful home-defending tyke Alex Pruitt and also cast a quartet of new crooks to replace the bumbling thieves played by Joe Pesci and Daniel Stern.
Did It Work?: Nope. Critics (who didn't much care for the first two entries) pilloried the film and audiences avoided it like the plague. Another reboot -- the TV-movie Home Alone 4 -- was attempted in 2002 with another kid playing Culkin's character Kevin McAllister, but it's deservedly forgotten.

Anacondas: Hunt for the Blood Orchid
Original Stars: Jennifer Lopez, Ice Cube, Jon Voight
Replacements: KaDee Strickland, Morris Chestnut, Johnny Messner
Reason For the Switch: The stars of the original went ahead and got super-famous, putting them out of the producers' price range.
Did It Work?: Kind of. Though the film grossed only half of the original's $65 million take, it proved there was enough of an audience for the franchise to allow it to continue on for two more made-for-TV sequels.

Son of the Mask
Original Star: Jim Carrey
Replacement: Jamie Kennedy
Reason For the Switch: Because the studio couldn't pay Carrey enough money to return for another outing as Stanley Ipkiss, leaving them to cast Kennedy as new mask-wearer Tim Avery, whose infant son also acquires special mask-related powers.
Did It Work?: Not a chance. Roger Ebert spoke for the majority when he wrote, "There may be a way this could be made funny, but Son of the Mask doesn't find it."

The Fast and the Furious: Tokyo Drift
Original Stars: Vin Diesel, Paul Walker
Replacements: Lucas Black, Bow Wow
Reason For the Switch: After Diesel bowed out of the sequel 2 Fast 2 Furious, producers decided to cut Walker loose as well and instead cast Black as a rebellious high-schooler who is exiled to Tokyo to live with his father and gets involved in the local drifting scene.
Did It Work?: The low grosses for Tokyo Drift almost ended the franchise for good. But when the original cast was reassembled for a Hail Mary fourth installment, audiences returned in droves. Apparently, we just can't quit Diesel, Walker and their homoerotic tension.

The Final Destination Movies
Original Stars: Devon Sawa, Ali Larter
Replacements: A.J. Cook, Mary Elizabeth Winstead, Bobby Campo, Nicholas D'Agosto
Reason for The Switch: Every chapter in the Final Destination series has featured a new crop of teens falling prey to elaborate death traps. (The one instance of carryover was when Larter popped up in Final Destination 2.) The producers realized early on that they could spend more money on said traps if they didn't have to pay the same actors to keep coming back over and over again.
Did It Work?: Yup, for five movies and counting.

Scream 4
Original Star: Neve Campbell
Replacement: Emma Roberts
Reason For the Switch: While much of the original Scream cast (including Campbell) does return for the fourth go-around, the movie devotes a lot of time to introducing a bunch of younger characters (including Roberts as Campbell's on-screen niece) who can carry on the series for future installments. 'Cause who under the age of 20 knows what the hell Party of Five is, right?
Did It Work?: The jury's still out. Prior to the movie's release, Wes Craven was speaking openly about plans for a new Scream trilogy. But disappointing box-office returns put that talk on hold. Still, if enough DVDs are sold, a Scream 5 with another all-new cast could still become a reality.