The Walking Dead cast surprises birthday girl Demi Lovato

Demi Lovato was left stunned after the cast of her favorite TV series The Walking Dead sent her video messages for her birthday.

The Skyscraper singer turned 24 on Saturday (20Aug16), and her loved ones decided to contact the stars of the hit zombie show to give her an unforgettable present in the form of a pre-taped video.

Lovato shared the clips on her Snapchat account, and in the footage, actor Andrew Lincoln and a man in a plastic lion mask serenaded the star with Happy Birthday, before the mystery person revealed himself to be co-star Norman Reedus.

Steven Yeun and Josh McDermitt also sent well wishes to Lovato, with the latter joking that he would be up for a date with the newly single star, using lyrics from her Cool For The Summer song to make his point.

"I do appreciate the female form," McDermitt said with a straight face. "And I'm just throwing it out there, to see if you wanna take me down to your paradise, and don't be scared!"

Lovato also expressed her excitement for the video on Twitter, writing, "I just got the best birthday video sent from the cast of the walking dead and I'm s**tting my pants".

Other messages came pouring in on social media from pals including Lucy Hale, Christian Siriano, Paulina Rubio, and Nick Jonas, who she's currently on tour with.

Nick's older brother Joe, who dated Demi back in 2010, also sent her a sweet tweet, writing, "Happiest of incredible birthdays to one of my best friends @ddlovato I'm so glad to have you in my life. Have the best one yet."

While he couldn't round up the members of The Walking Dead, he did manage to get the hundreds of fans at his DNCE concert in London to sing her Happy Birthday in a video posted on Twitter.