Katie Holmes is celebrating her 45th birthday in Capeside.
"Thank u so much!" she wrote under the post. "You are so kind always!"
Mary-Margaret's post included a throwback photo of the pair in the late ‘90s digging into a cupcake, and another more recent snap of the duo indulging in wine.
"In a world full of muffins … You are one sparkly cupcake," the 69-year-old—who played Dawson's mom Gail on The WB series—wrote in her birthday tribute. "Happy Birthday sweet friend @katieholmes. We love you so very much."
Mary-Margaret also included some heart and kissy emojis, and of course some call outs to their time on the drama series in the hashtags—including "TV Family" and "Forever Friends."
The duo has remained close in the 20 years since the series wrapped. Back in March, the on-screen mom went to see Katie in an off-broadway performance of The Wanderers with fellow Dawson's Creek costar John Wesley Shipp—who played her husband in the drama series.
"An amazing night watching our beautiful @katieholmes perform," the actress wrote at the time. "She was sensational as always!"
"Mary Margaret and John were such a huge and important part of #dawsonscreek I am so grateful to have worked with them and experience their kindness," she wrote on Instagram at the time. "Thank you for taking such good care of us. I love you both."
Mary-Margaret remains dedicated to spreading the love to all of her former costars. Earlier this month, she shared another throwback photo James Van Der Beek—whom she's also remained close to throughout the years.
"Every year since my mother died, @thereal_marymargarethumes makes me cookies and sends them to me on my birthday," the 46-year-old wrote on his Instagram in March. "I have the best TV momma on the planet."