Sarah Michelle Gellar

Not many 5 year olds get to witness a Buffy the Vampire Slayer reunion at their birthday parties, but on Tuesday, Sept. 17, Charlotte Prinze was an exception. The older daughter of Buffy star Sarah Michelle Gellar and Freddie Prinze Jr. was surprised with a private screening of the upcoming remake of Annie, and celebrity guests included Buffy costars Michelle Trachtenberg and Seth Green.

“Ssshhhhh don’t tell my daughter...But tomorrow I’m hosting a screening of the #AnnieMovie for her I might have to sing along,” Gellar, who played Joss Whedon’s most celebrated heroine, tweeted on Sept. 15.

Gossip Girl star Trachtenberg, who played Buffy’s little sister Dawn on the show, Instagrammed several images from the event, posing with her on-screen sis and writing, “#BuffyandDawn together again! Celebrating #CharlottesBirthday #DenimDuo #BTVS.”

Another Sunnydale resident showed up to celebrate, too: Seth Green, who played the beloved werewolf Oz, and his wife Clare Grant. Posing with the couple in a picture, Trachtenberg wrote, “When #Buffy calls, #DawnAndOz answer #CharlottesBirthday #AnnieMovie.”

The costars, who (with the exception of Green) participated in the fan-favorite musical episode “Once More With Feeling,” also posed in an Annie-themed frame, captioning the picture, “.@SethGreen @ClareGrant @RealMichelleT @RealFPJr #Maybe #Tomorrow will be a #hardknocklife but yesterday #easystreets.”