All play now includes an aspect of role playing. "I'm the shopkeeper and you're the dentist", "I'm the teacher and you're Bella at little school" or "I'm your baby and you're my mummy and mummy is my daddy."
You get the idea.
In the garden this afternoon I was Joe (easy enough), she was Layla and Bella was staying the night at Granny and Grandpa's. Bella (being Layla) went up into the house then popped her head out of the door a few minutes later and shouted at the top of her voice "LAYLA NEEDS A POO!"
I'll let the neighbours wonder - explaining would be too complicated.