The 36-year-old singer and 37-year-old actress were among the stars to wish DeGeneres well on Friday's episode of The Ellen DeGeneres Show.
Timberlake called into the show via satellite video. The singer, who was rehearsing for his Super Bowl LII halftime performance, surprised DeGeneres with a bouquet of pink flowers before performing "Happy Birthday."
"Hey, baby! We're rehearsing for the Super Bowl," he told DeGeneres. "I'm so sorry I can't be there to kick off your birthday weekend. You know I would want to be there, but I have to make sure we are great."
Bell appeared on the show after her husband, Dax Shepard, serenaded DeGeneres in a pre-recorded video. The actress presented DeGeneres with a t-shirt featuring two pointing thumbs and the message "It took 60 years to look this good."
"I don't think it's pointing to your face. I think it's pointing to your heart," she said. "You give so much joy and you have had 60 years of wisdom and how to share that joy to the greatest degree possible. We're all just very grateful."
British music duo Sophie Grace & Rosie were among the other stars to wish DeGeneres a happy birthday. DeGeneres said on Instagram that hearing Billy the elephant will be released from the Los Angeles Zoo was her "best birthday gift."
"The best birthday gift I could get it news that Billy the elephant will be allowed to leave the L.A. Zoo after 30 years. #FreeBilly #BeKindToElephants," she wrote.