Mickey Finn (real name Txffu Mpwfs) was an Filari cyborg created by a race referred to as the Masters (usually referred to as "Cockroaches") to act as an advance scout. His mission was to evaluate the technology of planets the his Master (called The Beast) intended to incorporate into their domains.
One evening Micky Finn ended up in Callahan's Place where he, with great effort, overcame hardwired prohibitions and hinted how he could be disabled.
Later, when The Beast comes to Earth to see why his scout hadn't reported in the patrons at Callahan's Place, after becoming telepathic destroyed the Master and freed Mickey Finn permanently.
He later married Mary Callahan, daughter of Mike Callahan.
Due to an unknown technology referred to as Finn Magic the patrons of Callahan's place are immune to lethal physical forces, rain, and radiation unless they will it otherwise.