I'm resurrecting this one because I am having the same issue. No layered images, just regular old pics:
define g = Character("Inspector Greenfield", color="#4b4efa", callback = name_callback, cb_name = 'gfield') image greenfield2 = At('greenfield2', sprite_highlight('gfield'))
I'm pretty sure it's the image definition since the character appears ("show greenfield2 at right") before he speaks. Should I be renaming the spright_highlighted image something else? But then what goes in the definition? I've gone around in circles on this a million times.