In order to wake Alex from a dissociative/mute/withdrawn episode I sometimes use songs that attract her attention and simultaneously offer a reward if she can repeat the song. Singing a funny song preferably with actions wakes her up. By the time she can sing the song properly she is ready to safely walk around.
This was our latest: (Sung to the tune of “You are My Sunshine”)
I am an Alex
A hungry Alex
Shut up Mummy
I am awake
I need Samosas
To fill my Tummy
Oh someone take my mother away!