I'll give you an example,
Vaginia Haye:
http://www.imdb.com/name/nm0382162/
http://www.virginiahey.com/
Most commonly seen looking like:
![Image](http://farscape.borderline-angel.com/Images/Zhaan/zhaan003.jpg)
Was actually that lass in Mad Max 2:
![Image](http://www.madmaxmovies.com/cast/MadMax2/VirginiaHey/SlideAndDice.jpg)
![Image](http://www.madmaxmovies.com/cast/MadMax2/VirginiaHey/VirginiaHey.jpg)
http://www.madmaxmovies.com/cast/MadMax2/VirginiaHey/
Keeping with the Mad Max motif, The Mouth of Sauron was also the helicopter pilot:
![Image](http://www.elvish.org/gwaith/movie/mouth_of_sauron2.jpg)
![Image](http://home.iprimus.com.au/ttguy/spence.gif)
Feel free to add any more of your own, usually a b-movie secondary character turns up in a tv series or a supporting role in a movie decades later.