Demi Lovato is full of surprises!
On Dec. 3, the "Neon Lights" singer took over the stage at 99.7's Triple Ho Show in San Jose with UK singer Jessie J. The duo sang the hit Jessie sings with Ariana Grande and Nicki Minaj, "Bang Bang."
Grande could not make the performance as she was performing at the Victoria's Secret Fashion Show in London that night, and when Lovato filled in, the audience went wild.
Lovato, 22, tweeted out her excitement to perform with Jessie J, 26.
Likewise, Jessie J tweeted back a thank you too and said that she's been wanting to sing with Lovato "forever."
The two certainly make a powerhouse duo, but this is not the only surprise Lovato gave this month.
Just yesterday, she made an unexpected performance of"Avalanche" on stage with Nick Jonas at KISS FM's Jingle Ball at the Staples Center in Los Angeles. Jonas and Lovato's duet brought the crowd to their feet.
Demi is a fan of surprising the audience, but even she gets surprised! Check out the video below to see how she was proposed to at one of her concerts.