Sarah played everyone's favourite demon hunting superhero Buffy Summers in the hit series, while Michelle was her onscreen younger sister Dawn.
And since the show wrapped back in 2003, they've remained firm friends.
Yesterday, a picture posted to Michelle's Instagram account showed the pair smiling for the camera while celebrating Sarah's daughter Charlotte's fifth birthday party.
The caption read: "#BuffyandDawn together again! Celebrating #CharlottesBirthday #DenimDuo #BTVS."
Aww, it's like they haven't changed!
Also joining the birthday celebrations was another familiar face to Buffy fans - Seth Green, who played werewolf / Scooby Gang member Oz.
A caption on that picture by Michelle said: "When Buffy calls, Dawn and Oz answer!"
The gang were back together to mark Charlotte's fifth birthday. Sarah and husband Freddie Prinze Jr. hosted a special screening of the Annie move for their little one.
Buffy The Vampire Slayer ran from 1997 until 2003.
Sarah, Michelle and Seth weren't the only Buffy stars enjoying a bit of a reunion lately. Earlier this month, Nicholas Brendon (Xander) and Emma Caulfield (Anya) were pictured together at a fan event in Australia, while Sarah was seen hanging out with Anthony Stewart Head (Giles) back in July.
Aww... what a show!