Miley Cyrus makes surprise appearance at ALS charity walk with Courteney Cox, Reese Witherspoon

A Miley Cyrus-certified surprise for a great cause? Sign us up.

The "Wrecking Ball" renegade made an appearance at this past weekend's 13th Annual L.A. County Walk to Defeat ALS, to support celebrity pilates instructor Mari Winsor -- who proceeded to "kick her ass" with a morning warm-up to Pharrell's "Happy."

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Sporting colorful galaxy leggings, a T-shirt covered in hearts and a prominent pink bow, Cyrus did not sacrifice her signature style to break a sweat.

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Hollywood power publicist Nanci Ryder also had stars like Reese Witherspoon and Courteney Cox studding the scene and participating to show their support. According to E!, Team Nanci was the day's top fundraising group.

See more of Miley Cyrus in the gallery below!

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