Jennifer Lopez surprised the crowd when she took the stage at We Day in Vancouver on Wednesday and performed a medley of her hits.

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The host of the night, Selena Gomez, introduced the superstar to the 20,000 attendees and commended her work as an activist. Lopez, whose entertainment career spans over 20 years, started the Lopez Family Foundation in 2009 along with her younger sister Lynda. The not-for-profit aims to increase health care and education for families that typically don't have such access.

"She created a foundation to help her empower underprivileged families and give them a chance at better health. She's here to inspire us to keep fighting for the causes we believe in," Gomez said.

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Lopez opened her set with her 1999 hit Let's Get Loud wearing a white coat. She then took off the outerwear to reveal a shiny Celia K body suit and performed 2011's On the Floor. The New York native shifted into Get Right (2005) and showed off her dance moves. The 45-year-old then performed her newest song Big Booty from her latest album A.K.A. and flaunted her famous asset.

 #WeDay

A photo posted by Jennifer Lopez (@jlo) on Oct 10, 2014 at 7:49pm PDT

"Congratulations We Day," she concluded about the event which aims to empower the younger generation. "You make the world a better place. And thank you so much for letting me be here and celebrating with you. I'm very proud of you all."

Other performers of the night included Nick Jonas, Shawn Mendes, Marianas Trench, Neverest, Kardinal Offishall and JRDN. For more information on We Day and upcoming events, visit WeDay.com.