Prince Harry surprises students by appearing at Toronto We Day event

Prince Harry surprised thousands of young people Thursday when he arrived unannounced at the Toronto We Day celebration.

Harry took the stage around lunchtime at Air Canada Centre, the host venue for the youth empowerment event.

The prince spoke about the importance of optimism in a cynical world.

There are a lot of scary forces in the world right now, he said, but hope for the future should remain the most important focus.

Harry touched specifically on environmental sustainability, telling the crowd that he understands their frustration about how "entrenched mindsets are not keeping pace with the urgency of the threats to our environment."

He also said he feels encouraged by how much young people value environmental causes.

The prince is in Toronto for the Invictus Games, the athletic competition for wounded military members that he founded in 2014. He took the stage following Invictus ambassador Rick Hansen, who toured the world in his wheelchair between 1985 and 1987 to raise money for spinal cord research.

After Hansen spoke, the crowd was told they were going to hear a recorded message from Prince Harry. When he came out onstage instead, he was greeted with enthusiastic cheers. Many of the audience members jumped up from their seats, and some even ran down from the aisles to try to get closer to the stage before they were stopped by security.

We Day holds events all over the world to encourage youth engagement in social causes. Singer Kelly Clarkson, actor Jacob Tremblay and sprinter Andre De Grasse were among the other speakers and perfomers at Thursday's show.

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