The girl I knew who was a pony played at break with her friends who were pretending to be ponies. They all did the same thing but she never switched it off. Except when sitting in a classroom desk.
Maybe there was something else wrong - someone on another board remembered a girl they were at school with who had a profound small animal identification - she later turned out to have been subject to sex abuse that her family and doctor thought she should 'get over'.
Abused, ND, unhappy about bodily changes, unhappy about family or household dynamic. Surely schools should be providing an alternative way to live and focus rather than reinforcing understandable but deranged self harm and bodily denial. See also anorexia, gender change, cutting. Again I recommend that Freeman interview, very good insights from someone who has gone through and survived an adolescent crazy phase.