Presto Change-O Phoebe
Two kids from Earth befriend a shapeshifting girl from another dimension, and discover an evil plot that threatens to destroy the multiverse.
The main character, Phoebe, is a girl from a parallel universe with incredible shapeshifting powers. She can transform various parts of her body into whatever weapons or equipment the situation calls for. After crash-landing in 21st century England, Phoebe befriends two kids named Emily and Jack, and together they set off to find out what caused her to arrive there—and to stop a villain who threatens both of their universes.