Sarah Hyland
Before she starred on Modern Family, Sarah Hyland co-starred in two separate episodes of the procedural law series, first as a child victim in 2001 and then later as killer Jennifer Banks in a 2009 episode.
Kathy Griffin
While we normally see Kathy Griffin as a funny lady, she took on a serious role for Law & Order: SVU when she played Babs Duffy, a lesbian rights group leader who accuses the police department of homophobia when, in her opinion, they are neglecting the murder case of a lesbian woman.
Adam Driver
Before he'd go on to play Kylo Ren, Adam Driver would co-star in both Law & Order as well as Law & Order: SVU, the latter of which saw him play a creepy IT worker who installed cameras in girls' apartments.
Ian Somerhalder
In 2003, Ian Somerhalder terrified us as Charlie Baker on the series, a spree killer who convinced his brother to kill couples before killing four people himself. Thankfully, he was caught by Olivia Benson in the end.
Bradley Cooper
Before he starred in The Hangover and A Star is Born, Bradley Cooper starred in two Law & Order crossover episodes as the defense lawyer for a serial rapist.
Hilary Duff
Hilary Duff's role on the series was compelling but sad, playing a mother who panicked and buried her daughter after she contracted measles from an unvaccinated classmate.
Brittany Snow
Brittany Snow's guest star role was small but memorable when she played Jamie Hoskins, a young woman who accidentally killed a 14-year-old when she attempted to kill herself by running a car into a building but instead hit a crowd of people. When it turns out that she did so while on bipolar medication, her case attracts the attention of rock star Derek Lord, who was played by none other than...
Norman Reedus
Norman Reedus, of The Walking Dead fame! In the same episode with Snow, Reedus' plays a charismatic rock star who has strong views against the pharmaceutical industry's use of medications for mental illnesses and brings them to Jamie Hoskins' court case.
John Stamos
John Stamos played a reproductive abuser who impregnated dozens of women, leading to a pretty grisly end for his character when one of his victims finds out what he's been doing.
Serena Williams
The tennis star played Chloe Spiers in a season five episode where she was a victim of Internet porn.
Milo Ventimiglia
Before he'd go on to capture our hearts in This Is Us, Milo Ventimiglia had a small role on the long-running show in 2003 playing a victim of a child molester.
Whoopi Goldberg
Whoopi Golberg shocked us all in her dark role as Chelsey Watkins, a foster mother who manipulates her foster children into robbing homes and committing murders.