They bring life to the plot and help keep the show relevant and viewers on their toes.

To keep things interesting, well-known faces took over the show for one or even a handful of episodes.

For eight episodes, he kept coming back to threaten the livelihood of everyones hero.

Guest stars on Law & Order: SVU.

Merritt Rook is one of those.

When dealing with multiple personalities, not all viewers agreed with how it was portrayed.

Nixon took Janis Donovan and owned her for 42 minutes.

Pablo Schreiber as William Lewis on Law & Order: SVU.

As controversial as the episode can be, no one can deny the talent is there.

Her connection to Detective Stabler stands out in this episode.

And just like it is usual for her, her portrayal of Birdie Sulloway did not disappoint.

Robin Williams as Merritt Rook on Law & Order: SVU, “Authority."

Her chemistry withMatthew Lillardtook her performance to another level.

Until the last minutes of the episode, you still do not know how to feel about her.

That is the magic of Burnett: she can always humanize every character she plays.

Cynthia Nixon as Janis Donovan on Law & Order: SVU, “Alternate."

Many fans remember her appearance because it made Benson question how others see her.

Do you ever get a gay vibe from me?

Greg Yates claimed his place close to William Lewis as one of the most hated characters inSVUhistory.

Carol Burnett as Birdie Sulloway with Olivia Benson (Mariska Hargitay) and Elliot Stabler (Chris Meloni) on Law & Order: SVU, “Ballerina."

Robertss acting made viewers feel disgusted with every word he said.

Although his storyline was created onCPD, his character developed more as he established a relationship with Detective Rollins.

This connection and Robertss excellent characterization allowedKelli Giddishs character to grow professionally, earning more of Bensons trust.

Kathy Griffin as Babs Duffy on Law & Order: SVU, “PC."

Viewers hated him from the moment he showed up until the last minute.

Ken Turner is supposed to be a charming, rich man who gets any woman he wants.

But as the episode advances, the audience realizes he is hiding something.

Dallas Roberts as Greg Yates on Law & Order: Special Victims Unit.

She did not disappoint.

The rape backlog is an issueMariska Hargitayis constantly trying to bring awareness to through their storylines.

Vicki Sayerss story does just that.

John Stamos as Ken Turner on Law & Order: Special Victims Unit, “Bang."

Jennifer Love Hewitts performance is immaculate and makes the audience go through every emotion with her.

The fear, pain, disappointment, and final breath of relief.

You go through everything with her and the detectives.

Jennifer Love Hewitt as Vicki Sayers on Law & Order: Special Victims Unit, “Behave."

That is whatEric McCormackdid when he joinedSVUfor Sugar during season 11.

He played Vance Shepard, someone viewers were ready to hate but ended up understanding on a deeper level.

Shepard ends up being a father protecting his daughter, trying to the right all his wrongs.

Eric McCormack as Vance Shepard on Law & Order: Special Victims Unit, “Sugar."

However, he cannot do so and dies in the middle of the squad room.

McCormack gave the audience a memorable performance far from what they were used to when he played Will Truman.

Van Der Beek does a great job getting the audience to hate him and root for his demise.

James Van Der Beek as Sean Albert on Law & Order: Special Victims Unit, “Father Dearest."

From the moment he shows up on the screen, you know something is wrong with him.

As the episode develops, Van Der Beeks acting captivates the fans who want to see where this ends.

He proved he is no longer a kid but a grown actor who can play multifaceted characters.

Law and Order: SVU

KEEP READING:Best Benson And Stabler Episodes On ‘Law & Order: SVU.’