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."
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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Miley Cyrus makes surprise appearance at ALS charity walk with Courteney Cox, Reese Witherspoon
NEW YORK, NY - MAY 13: Miley Cyrus performs at the 2015 Adult Swim Upfront Party at Terminal 5 on May 13, 2015 in New York City. (Photo by Dimitrios Kambouris/Getty Images for Tuner)
NEW YORK, NY - MAY 04: Miley Cyrus attends the 'China: Through The Looking Glass' Costume Institute Benefit Gala at the Metropolitan Museum of Art on May 4, 2015 in New York City. (Photo by Dimitrios Kambouris/Getty Images)
CLEVELAND, OH - APRIL 18: Miley Cyrus speaks onstage during the 30th Annual Rock And Roll Hall Of Fame Induction Ceremony at Public Hall on April 18, 2015 in Cleveland, Ohio. (Photo by Mike Coppola/Getty Images)
LAS VEGAS, NV - MARCH 22: Entertainer Miley Cyrus makes an appearance at Omnia Nightclub at Caesars Palace on March 22, 2015 in Las Vegas, Nevada. (Photo by Ethan Miller/Getty Images)
LOS ANGELES, CA - FEBRUARY 20: Recording artist Miley Cyrus, wearing TOM FORD, attends the TOM FORD Autumn/Winter 2015 Womenswear Collection Presentation at Milk Studios in Los Angeles on February 20, 2015. (Photo by Michael Buckner/Getty Images for Tom Ford)
LOS ANGELES, CA - FEBRUARY 07: Actor Jamie Foxx (L) and recording artist Miley Cyrus take a selfie at the Pre-GRAMMY Gala and Salute To Industry Icons honoring Martin Bandier at The Beverly Hilton Hotel on February 7, 2015 in Beverly Hills, California. (Photo by Larry Busacca/Getty Images)
LOS ANGELES, CA - JANUARY 09: Actress/singer Miley Cyrus attends the W Magazine Shooting Stars Exhibit Opening at Wilshire May Company Building on January 9, 2015 in Los Angeles, California. (Photo by Alberto E. Rodriguez/Getty Images)
MIAMI, FL - DECEMBER 05: Singer/songwriter Miley Cyrus attends Haute Living presents Hublot ÂTime Is BeautifulÂ at the estate of JR and Loren Ridinger on December 5, 2014 in Miami, Florida. (Photo by Dimitrios Kambouris/Getty Images For Hublot)
PERTH, AUSTRALIA - OCTOBER 23: Miley Cyrus performs her Bangerz Tour live at Perth Arena on October 23, 2014 in Perth, Australia. (Photo by Paul Kane/Getty Images)
SYDNEY, AUSTRALIA - OCTOBER 13: Miley Cyrus performs live for Sunrise at Sydney Opera House on October 13, 2014 in Sydney, Australia. (Photo by Don Arnold/Getty Images)
NEW YORK, NY - SEPTEMBER 10: Designer Jeremy Scott (L) and Miley Cyrus pose baskstage at Jeremy Scott fashion show during MADE Fashion Week Spring 2015 at Milk Studios on September 10, 2014 in New York City. (Photo by Chelsea Lauren/Getty Images)
Miley Cyrus poses in the press room at the MTV Video Music Awards (VMA), August 24, 2014 at the Nokia Theatre in downtown Los Angeles. AFP PHOTO / Frederic J. Brown (Photo credit should read FERDERIC J. BROWN/AFP/Getty Images)
American pop singer Miley Cyrus performs during her concert at the Ericsson Globe Arena in Stockholm, Sweden, on May 30, 2014. AFP PHOTO / TT / MAJA SUSLIN ***SWEDEN OUT*** (Photo credit should read MAJA SUSLIN/AFP/Getty Images)
HOLLYWOOD, CA - JANUARY 28: Recording artist Miley Cyrus performs onstage during Miley Cyrus: MTV Unplugged at Sunset Gower Studios on January 28, 2014 in Hollywood, California. (Photo by Christopher Polk/Getty Images for MTV)
BEVERLY HILLS, CA - JANUARY 25: Recording artist Miley Cyrus attends the 56th annual GRAMMY Awards Pre-GRAMMY Gala and Salute to Industry Icons honoring Lucian Grainge at The Beverly Hilton on January 25, 2014 in Beverly Hills, California. (Photo by Larry Busacca/Getty Images for NARAS)
LAS VEGAS, NV - DECEMBER 27: Entertainer Miley Cyrus arrives at the grand opening of Britney Spears' two-year residency 'Britney: Piece of Me' at Planet Hollywood Resort & Casino on December 27, 2013 in Las Vegas, Nevada. (Photo by Ethan Miller/Getty Images)
SUNRISE, FL - DECEMBER 20: Miley Cyrus performs onstage during Y100's Jingle Ball 2013 Presented by Jam Audio Collection at BB&T Center on December 20, 2013 in Sunrise, Florida. (Photo by Alexander Tamargo/Getty Images for Clear Channel)
NEW YORK, NY - DECEMBER 13: Miley Cyrus attends Z100Âs Jingle Ball 2013, presented by Aeropostale, at Madison Square Garden on December 13, 2013 in New York City. (Photo by Bryan Bedder/Getty Images for Clear Channel)
LOS ANGELES, CA - DECEMBER 06: Recording artist Miley Cyrus performs onstage during KIIS FMÂs Jingle Ball 2013 at Staples Center on December 6, 2013 in Los Angeles, CA. (Photo by Christopher Polk/Getty Images for Clear Channel)
LOS ANGELES, CA - DECEMBER 06: Singer Miley Cyrus attends KIIS FMÂs Jingle Ball 2013 at Staples Center on December 6, 2013 in Los Angeles, CA. (Photo by Rich Polk/Getty Images for Clear Channel)
Miley Cyrus performs onstage during the MTV EMA's 2013 at the Ziggo Dome on November 10, 2013 in Amsterdam, Netherlands. (Photo by Gareth Cattermole/Getty Images for MTV)
NEW YORK, NY - OCTOBER 22: Miley Cyrus attends the 30th Annual Night Of Stars presented by The Fashion Group International at Cipriani Wall Street on October 22, 2013 in New York City. (Photo by Dave Kotinsky/Getty Images)
NEW YORK, NY - OCTOBER 08: Miley Cyrus visits 'Late Night With Jimmy Fallon' at Rockefeller Center on October 8, 2013 in New York City. (Photo by Jamie McCarthy/Getty Images)
Singer Miley Cyrus arrives at the MTV Video Music Awards August 25, 2013 at the Barclays Center in New York. AFP PHOTO/Emmanuel DUNAND (Photo credit should read EMMANUEL DUNAND/AFP/Getty Images)