That comparison first appeared in the Attack of the Clones shooting script during a scene with Anakin and Watto.
Watto calls Anakin a "little womp rat" before remarking that he "sure sprouted." What did he mean?
Is Watto literally calling him a dwarf, or is it a term of endearment on Tatooine?
Edit: I'm referring to the way Watto used womp rat.
Edit 2 - exact dialogue:
WATTO (continuing in English) You are Annie! It is you! You little womp rat!
WATTO gives ANAKIN a big hug.
WATTO (continuing) Ya sure sprouted! Weehoo! A Jedi! Waddya know? Hey, maybe you couldda help me wit some deadbeats who owe...