Here's one from the UK made by a mum who says that the eyes, ears and hands are mini doughnuts, the arms are marshmallows, legs and shoes are Swiss rolls:
Here's one looking a wee bit worried from the blog archive of Beth Soderland:
From Ciao Annie comes this robot cake in which they embedded a light box into the top of the robot's head.
I think that the appeal lies with the faces and all those coloured buttons and dials. They are so silly looking and at the same time so "human".
Lots of robots here - some with lights: