Mila Kunis, Ashton Kutcher join Wilmer Valderrama for 35th birthday party

LOS ANGELES, Feb. 2 (UPI) -- Mila Kunis and Ashton Kutcher joined their That 70s Show co-star Wilmer Valderrama on Jan. 29 for the actor's 35th birthday party.

According to People magazine, the event -- which took place at Palms Thai restaurant in Hollywood -- was a surprise planned by Valderrama's girlfriend, singer Demi Lovato.

"He was laughing and saying that he had expected a quiet dinner," an insider told the magazine.

Valderrama -- whose actual birthday was Jan. 30. -- shared a picture from the custom-made cake he had that evening on Twitter and returned to the social media site Sunday to thank Lovato and his friend Tadao Salima for a "special birthday."

Lovato, 22, and Valderrama have been dating on-and-off since 2010. While the couple has kept their relationship outside of the public eye for most of the time the two recently began sharing pictures together on social media.

Since rising to fame in the late '90s sitcom, Valderrama has had several television roles and is slated to star in a number of movies including To Whom It May Concern, The Adderall Diaries and Castro's Daughter in 2015.