Phoebe Spengler, played by McKenna Grace, is a character in the film Ghostbusters: Afterlife.
Phoebe moves to Summerville, Oklahoma, after Callie is evicted from their apartment. They live on the farm of their estranged grandfather, who Phoebe never knew. Phoebe is highly intelligent and has a scientific mind. She is able to hold a conversation with Gary Grooberson about the strange seismic events in Summersville.
After finding a PKE Meter, Phoebe follows its readings and discovers a hidden ghost trap and a bunker with a Proton Pack. After brining the trap to school, Gary tries to power it up and inadvertently releases one of Gozer's guardians.
After repairing the Proton Pack, she and her friend Podcast test it out in the yard. They discover a ghost who eats metal in the barn. She attempts to catch him but Podcast is unable to trigger the trap in time and it gets away. They try to track it down as Trevor, who was able to get the Ecto-1 running, finds them on the highway. The three of them go to downtown Summerville and find the ghost who Podcast names Muncher. They destroy a lot of public property before finally chasing Muncher down, who was making its way to the Gozer Temple. They trap it, but on the way home are pulled over and arrested.
Phoebe uses her one phone call to contact Ray Stantz who she manages to tell she is Egon's grandaughter before her phone time is up. After Callie takes her and Trevor home, Phoebe is outraged she was never told that Egon, a scientist, Ghostbuster, and hero, was her grandfather.
When Callie and Gary are possessed by Zuul and Vinz Clortho, Phoebe, Podcast, Trevor, and Trevor's crush Lucky Domingo team up to stop Gozer. Her phonecall worked, as Peter Venkman, Ray Stantz, and Winston Zeddemore arrive to assist Phoebe and her friends. Just as Gozer was overpowering the Ghostbusters, the ghost of Egon came along and assisted Phoebe and they managed to finally stop Gozer.
After stopping Gozer, the other three Ghostbusters, Trevor, Phoebe, Callie are all able to tell him goodbye before he moves on into the afterlife.