Jennifer Garner was almost in tears during a surprise celebration of her own only days after her ex-husband Ben Affleck asked Jennifer Lopez to marry him. The mom-of-three took to Instagram with an emotional video which left fans in disbelief. MORE: Jennifer Garner breaks silence after Ben Affleck and Jennifer Lopez's engagement In the clip, Jennifer celebrated her 50th birthday a few days early and her gift was amazing. WATCH: Jennifer Garner sparks engagement rumors with huge ring As the Yes Day actress enjoyed lunch at a plush-looking restaurant, she was surprised by none-other-than, legendary performer, Donnie Osmond. Jennifer appeared close to tears as he sat next to her and began to sing. DISCOVER: Jennifer Lopez and Ben Affleck's family member speaks out following their engagement newsPHOTOS: Jennifer Garner's dreamy $14m LA mansion near Ben Affleck – insideShe explained the scene in her caption which read: "My first (pre)birthday surprise was a doozy — the one and only, legend in his own time, object of my childhood adoration and devotion — @donnyosmond showed up to knock my purple socks off. A post shared by Jennifer Garner (@jennifer.garner)Jennifer was stunned by her birthday surprise! "He took an hour and a half of his day to sit with me, sing my favorites, and to give me a master class on how to be a class act."Her fans were almost as blown away by the moment as Jennifer was and they commented: "I don't believe it.