Kellie Martin joined the "ER" cast during Season 5 and became an instant fan favorite. She played Lucy Knight, a plucky young intern with an aptitude for caregiving. If you're anything like us, you're probably still processing Lucy's brutal, shocking exit from the show. As it turns out, Martin left "ER" partly due to tragic real-life circumstances.

A week before Martin started on "ER," her sister, Heather, died from lupus. On an episode of the "I Think You're Interesting" podcast, the actor admitted, "Being in a hospital after having been in a hospital for months for real with my sister was super weird and felt really wrong. I never allowed myself to really enjoy it and go there" (via Vox). With encouragement from her husband, Martin pulled it together for two iconic seasons on "ER." However, her sister's death took an enormous toll, and she ultimately decided to leave the show.

Martin also revealed that her "ER" co-stars only learned about her departure after reading the script. Alex Kingston (Dr. Corday) sobbed while she and Martin filmed their final scene together. Martin recalled, "It was hard, and my last scene that I ever shot on 'ER' was when I was laying on the slab dead, and the director, Jonathan Kaplan, came up, and he whispered to me, 'You're wrapped,' and I just grabbed my husband's hand, and I left. I didn't even say goodbye to people. It was really hard for me."