Batman interrogates insane drug user Bob Overdog at Arkham Asylum. Overdog pleads innocent of killing his confederates, blaming the incident on a diminutive elf called Bat-Mite. Batman disbelieves his story, suspecting that everything Overdog claims to have seen was nothing more than the effects of abundant drug use.
http://dc.wikia.com/wiki/Batman:_Legends_of_the_Dark_Knight_Vol_1_38

This would be a fun cgi filled movie!