"The Golden Girls" star celebrated her big day on Friday, January 17, and Sandra and Ryan, who appeared alongside the star in 2009's "The Proposal", took to Instagram with the sweet clip.
In the video, the pair amusingly compete with their birthday wishes, battling over which "loves you more" to the tune of Happy Birthday to You.
"Happy birthday dear Betty, from Sandy who loves you more than Ryan," Sandra begins.
"From Ryan, who loves you so much more than Sandy," he continues, adding, "Did she show up and hand-deliver flowers for you wearing nothing but black socks and a dozen gold bracelets just like you requested? Doubt it."
As the song comes to a close, a graphic flashes onscreen, reading,"Happy 98th Birthday Betty!"
Speaking to Parade magazine in 2018, Betty credited optimism for her long life, remarking: "I know it sounds corny, but I try to see the funny side and the upside, not the downside. I get bored with people who complain about this or that. It's such a waste of time."