Blaine is Lillith's half-brother, the black sheep of the family (Lilith being "the good one"), and has a sizeable, substantiated reputation as a con artist. Prior to his appearance in Frasier, he had tricked money out of people in Maine using the alias "Brad Cunningham", in Louisiana as "Royce Thibideaux" and in Albuquerque, New Mexico as "Santana Del La Cruz". He also sold forged autographs of famous people at one time; a wheeze which ended when it was discovered that his Marie Curie and Sugar Ray Robinson signatures had the same handwriting. He also fenced fake handicap plates.
Blaine appears to have conned Frasier several times; he sold him a fake deed for a 50,000-acre kelp farm, and once stole an antique salt server. He was said to have once posed as Frasier for a year, during which time he "treated" some of the latter's patients.
Blaine is reunited with Frasier in a single on-screen appearance, during which he claimed to have mended his ways. He explained that he had been involved in a car accident while drink-driving, and was subsequently paralyzed from the waist down; at the time, he backed this up by demonstrating an apparent immunity to pain, stabbing himself in the thigh with a brooch borrowed from Daphne.
He claimed to have had a "religious experience", which encouraged him to change his ways, and stated that he needed donations, including one thousand dollars in to cover hall rental costs for a Sunday session at a local hotel. Fraiser refused to give him the money, although later it is revealed that both Daphne and Niles did. Frasier attempted to contact Dr. Keigan, Blaine's "supposed doctor", in Laughlin, Nevada, who was unavailable at the time.
Later, Frasier interrupted Blaine's sermon, trying to convince people of his true nature. He pushed Blaine out of his wheelchair onto the stage, in an attempt to expose his charade; while Blaine lay on the stage, apparently unable to move, Frasier received a follow-up call from Dr. Keigan, who confirmed Blaine's story. Frasier performed an about-face and, in addition to helping Blaine back into his wheelchair and encouraging the audience to donate to his ministry, also promised to match any donations.
Returning to Frasier's apartment, Frasier gave Blaine the disputed salt server as a sign of good faith, before the latter departed. He then learned that Blaine had told Martin he had "mopped in a soup kitchen", "read for bed-ridden war veterans", and "visited the Galapogos islands to rinse spill oil off birds", all activities which a skeptical Frasier had previously suggested Blaine might use as "evidence" of his conversion.
Realizing that he had been fooled once more, Frasier darted outside, and was confronted with Blaine's empty wheelchair.