For the record, I thought Deep Breath was a solid start for the 12th Doctor and I'm looking forward to enjoying Capaldi's prickly, all business Time Lord.

4. The First Doctor - Doctor Who: 

To celebrate the 20th anniversary of the original run of Doctor Who, a feature episode was produced in 1983.

The Five Doctors was to reunite all five lead actors. Unfortunately, Tom Baker refused to participate so footage from the unaired story Shada was slotted in instead.

The original Doctor William Hartnell had passed away in 1975 and was replaced by Richard Hurndall.

 Although endorsed by Hartnell's widow, Hurndall’s portrayal of the acerbic first Doctor is the least believable aspect of the special, despite the wobbly sets and rubbery aliens. Hurndall passed away in the same year, supposedly before he was paid for the role.

3. Catwoman - Batman:

 If Batman is the world's greatest detective, why was he incapable of noticing when his arch nemesis Catwoman changed from white actress Julie Newmar to black cabaret songstress Eartha Kitt in the campy TV series which ran from 1966-1968?

Catwoman even changed again to the white Lee Meriwether for the movie. I suppose she was wearing a mask.

2. Becky - Roseanne: 

For the first five seasons of Roseanne Barr's sitcom, daughter Becky was played by Lecy Goranson. 

When the actress chose to pursue university, her character was written out of the show.

By season six, the role was recast with Sarah Chalke (later of Scrubs fame) who continued until the end of season seven, when Goranson's university schedule allowed her to return.

Scheduling conflicts midway through season eight resulted in Becky being played by both actresses in different episodes. Chalke reclaimed the role full time for the show's ninth and final season. 

The show’s producers dealt with the regular changes in Becky's appearance with a running gag.  

1. Jan Brady - The Brady Bunch:

When the cast of The Brady Bunch were approached in 1976 to return to television in the all singing, all dancing, all terrible Brady Bunch Variety Hour, all were coaxed back with the exception of Eve Plumb (Jan) who wisely stayed away.

She was replaced by "Fake Jan" Geri Reischl, a talented singer and actor. Luckily for everyone involved, and TV audiences, the show only lasted nine episodes and is considered one of the worst ever produced.

Reischl retired in 1983, but returned to singing in 2000. My brother bought me an autographed copy of her 2011 album, entitled 1200 Riverside for my birthday last year. It is not very good, but the CD makes a great drink coaster.