Sierra's Oscar Story Includes George Clooney, Cameron Diaz

Sierra Plys slept late on Monday. After all, she had a big night Sunday. Good thing she's home-schooled. Then again, maybe it's too bad because she could sure drop a few names in front of her classmates.

Sierra, an 11-year-old Rancho Santa Margarita girl who is a member of the Southern Calfornia Children's Choir, of the Academy Awards on Sunday night, providing background vocals to Esperanza Spalding on the Louis Armstrong song, "What a Wonderful World."

Butterflies? You bet. But no doubt they were fluttering a little more confidently knowing that one of America's favorite leading men had Sierra's back.

"On a commercial break, while waiting on stage to begin singing, George Clooney began talking to (five or six of us on the stairs), telling us that we didn’t need to be nervous and that he would sing with us if needed," Sierra said.

That wasn't her only Oscar-worthy moment.

"Then Cameron Diaz leaned over to me and told me that I looked so cute with my curly hair," Sierra said. "It was quite overwhelming, but I would do it again in a heartbeat. I could have cried while singing, because it felt so wonderful up there, knowing that my parents, family, and friends were watching from all around, and to see everyone in the audience smiling at us was powerful."

Not only did she feel the power of an audience while she was singing—and let's face it, having Clooney sing along a few feet from you is pretty cool—but also when it was over.

"When we finished the song, the audience clapped for a while, stopped and then began clapping again," she said. "It felt amazing."

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It was , to be sure. Parents Nicole and Allan Plys got their daughter to the departing point with plenty of time to spare (for picture-taking) and she left on board a bus from near South Coast Plaza at about 3 p.m. for the show. Parents were not allowed to accompany their kids to the big event, and the Plyses—including daughter Cadence, 5—spent the evening at friend Greg Swain's house in Lake Forest watching the telecast.

According to the schedule, the group was supposed to arrive camera-ready—dressed, made up, full of confidence—and perform at 8:01 p.m. They were to depart immediately after the performance from the Hollywood and Highland Center. They returned home about 9:45 p.m.

The performance can be heard here.

Sierra didn't get any serious face time during the show, but her mom—who knew exactly where to look—said she saw her daughter in a long shot. "Most of our friends are saying they didn't see her," Nicole Ludwig-Plys said. "My mom saw her also, so that's good enough for me."

Nicole has acted previously, in background roles in movies such as Cellular, Wedding Crashers and Sister Act II, and her daughter's big day wasn't lost on Mom.

"I used to act in movies in the past and have actually worked with some of the stars that she saw, so I know what it feels like to be in that environment and how exciting it is," Nicole said. "There are no words to describe the feeling you get when living in that moment, but yesterday was a gift and I want her to cherish it for the rest of her life."

For her participation, Sierra received an official cap commemorating the 84th Academy Awards, though it's really secondary.

"I had the most amazing time and I saw so many familiar faces that I have watched on the big screen over the years," Sierra said. "I normally do not get nervous, but seeing so many stars all together brought butterflies to my stomach for the first time in a long while."

For an even longer while, she'll remember this experience of a lifetime.