Every celeb who's served as a judge on 'American Idol'

When viewers said goodbye to "American Idol" two years ago, everyone believed it was the end of an era — but it turns out the show must go on. Fans were delighted and surprised when, in 2017, TV execs announced that "Idol" would be returning in 2018. This newest season will be judged by R&B icon Lionel Richie, who served as a guest judge in 2003, plus country singer Luke Bryan and pop superstar Katy Perry, who served as a guest judge in 2010. In celebration of the "American Idol" premiere on March 11, Wonderwall.com is taking a look at all of the stars who have served as judges on the show. Keep reading to see which celebs judged contestants on "American Idol"…

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Jennifer Lopez joined "American Idol" for Season 10 in 2011. Though the A-list star said she enjoyed judging the show, she decided to leave after two seasons. J.Lo wasn't done with "Idol" yet, however, and returned to judge seasons 13, 14 and 15 before leaving for good in 2015 once the series concluded.

RELATED: "American Idol" contestants: Where are they now?

Paula Abdul is one of the original "American Idol" three! The '80s pop star joined the show as a judge when it debuted in 2002. Audiences came to know and love Paula as the sweet judge on the panel and during her tenure alongside with judges Simon Cowell and Randy Jackson, she grew into a pop culture phenomena. All good things must come to end, however, and Paula chose to leave the show before Season 9 in 2010 due to a contract dispute.

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Comedian and talk-show host Ellen DeGeneres tried her hand at judging when she joined the "American Idol" panel in 2010 following Paula Abdul's exit. Ultimately, Ellen felt the show wasn't the "right fit" for her and left after only one season. She later said on Howard Stern's SiriusXM show in 2015 that "Idol" was one of the biggest mistakes of her career. "That's one of the worst decisions I've made," Ellen revealed.

The original mean judge, music executive Simon Cowell, joined "American Idol" when the show debuted in 2002 and quickly earned a reputation as a cut-throat and majorly blunt critic. The Brit held nothing back, often calling out contestants for being "utterly horrendous." Simon's reign of mean honesty came to an end when he exited the show to launch the U.S. version of "The X-Factor" in 2010.

Steven Tyler joined the "American Idol" judging panel for Season 10 in 2011. The Aerosmith frontman stayed for two seasons before departing in 2012. "After some long, hard thoughts, I've decided it's time for me to let go of my mistress 'American Idol' before she boils my rabbit," Tyler said in a statement at the time. "I strayed from my first love, Aerosmith, and I'm back… 'Idol' was over the top fun, and I loved every minute of it. Now it's time to bring rock back."

Randy Jackson was the final piece of the puzzle on the original "American Idol" judging panel. The bassist and music producer joined the show when it debuted in 2002 and stayed on longer than any of the other original judges. He transition from the judging panel to a role as an in-house mentor during Season 13 and officially left the show in 2014. He's one of the greatest "Idol" judges ever, dawg.

Yes, R&B's No. 1 diva, Mariah Carey, was an "American Idol" judge. The pop icon joined the show for Season 12 in 2013 and famously feuded with fellow judge Nicki Minaj throughout the season (remember those leaked tapes of their fights?!). Mariah ultimately decided to leave the show after one season to focus on her music full-time.

Rap's No. 1 diva, Nicki Minaj, also joined "American Idol" as a judge for Season 12 in 2013. The rapper was heard cursing Mariah Carey during auditions in Charlotte, North Carolina, before the season even premiered. Nicki allegedly said that if she "had a gun, I would shoot [Mariah]." Luckily, the feud ended when Nicki, like Mariah, chose to leave "Idol" after one season to focus on her music.

Country music star Keith Urban joined "American Idol" as a judge for Season 12 in 2013. He avoided all the drama and catfights during his debut season and really connected with audiences. Nicole Kidman's hubby stayed on for the remainder of the show's run, leaving only when "Idol" ended in 2016.

Grammy-nominated singer, songwriter and producer Kara DioGuardi was added as a fourth judge during Season 8 of "American Idol" in 2009. She stuck around for two seasons before leaving in 2011 to focus on her songwriting career as well as motherhood.

Harry Connick Jr. was the last full-time judge to be added to the original "American Idol" show. The jazz singer joined in 2014 and stayed for three seasons until "Idol" stopped airing in 2016.

Bee Gees singer Robin Gibb was never a full-time "American Idol" judge, but he did guest judge during Season 2 in 2003. Unfortunately, the music icon wasn't able to return to the show before he succumbed to cancer in 2012.

Disco queen Donna Summer served as a guest judge during the final rounds of Season 3 of "American Idol" in 2004. The "Last Dance" singer also mentored contestants while on the show.

Who knew Quentin Tarantino knew anything about singing? The filmmaker served as a guest judge and mentor during the final rounds of Season 3 of "American Idol" in 2004.

KISS lead singer Gene Simmons ditched the makeup and joined "American Idol" as a guest judge during Season 4 in 2005.

The winner of the first season of "American Idol" — and one of the most successful contestants ever, Kelly Clarkson — returned to the show as a guest judge during Season 9 in 2010.

Rap icon LL Cool J taught contestants to "knock out" the competition when he served as a guest judge during Season 4 of "American Idol" in 2005.

"Foolish Games" singer Jewel imparted her music wisdom to "American Idol" contestants when she served as a guest judge during Season 6 in 2007.

R&B songstress Mary J. Blige gave guidance to the "American Idol" contestants as a guest judge during Season 9 in 2010.

"Grease" alum Olivia Newton-John joined "American Idol" as a guest judge during Season 6 in 2007.

Queen of country pop Shania Twain had plenty of knowledge to share as a guest judge during Season 8 of "American Idol" in 2009.

"A Series of Unfortunate Events" actor Neil Patrick Harris served as a guest judge during Season 9 of "American Idol" in 2010.

"Complicated" singer Avril Lavigne critiqued contestants as a guest judge during Season 9 of "American Idol" in 2010.

"American Idol" runner-up Adam Lambert — one of the more successful "Idol" alums in history — served as a guest judge during Season 14 in 2015.

Former Spice Girl Victoria Beckham showed contestants how to keep it posh when she served as guest judge during Season 9 in 2010.

Former teen idol and Jonas Brothers alum Joe Jonas joined "American Idol" as a guest judge during Season 9 in 2010.

Tony Award-winning actress and singer Kristin Chenoweth served as a guest judge on "American Idol" during Season 9 in 2010.