For her guest appearance on Law & Order: Los Angeles, Lost alum Rebecca Mader not only had to push herself emotionally, but also had to push herself physically, withstanding long hours in the make-up chair for her role as a pregnant hit-and-run victim.

"The makeup was amazing," Mader says.  "I think that day that we shot all the makeup stuff, it was like a 17-hour day so I was either on set ... or basically getting the prosthetic done."

Check out photos of Rebecca Mader

Check out this behind-the-scenes video:

Law & Order: Los Angeles airs Wednesdays at 10/9c.