Jason Alexander has a criminal mind

As George Costanza, the balding bumbler on "Seinfeld," Jason Alexander was all about bringing the funny. But in tonight's episode of “Criminal Minds,” the actor is all about bringing the pain.

The latest installment of the CBS procedural features Alexander in dramatic makeover mode, portraying a deranged professor who claims to have killed several women and who puts a terrified mother in peril as part of his personal vendetta against serial killer profiler David Rossi (Joe Mantegna).

Putting on a shoulder-length white wig and a lullaby voice for an extra degree of sinisterness, Alexander is almost unrecognizable in the role.

"This guy is truly messed up, but I didn't approach it with that kind of judgment," Alexander said in an interview last week. "It's more interesting to look at the thing that has made this guy this angry -- I approach as if the character's agenda is righteous and pure. Otherwise, you fall into the trap of just playing a villain."

Alexander is the latest in a growing parade of unlikely performers -- primarily comic actors -- who are embracing their dark sides on "Criminal Minds." The drama, which centers on the search for demented serial killers by the Behavioral Analysis Unit of the FBI, is one of the network's most reliable and popular hits, frequently landing among the 10 highest-rated series.

Jamie Kennedy, best known for his "punks" on "The Jamie Kennedy Experiment" and outrageous characters in films such as "Malibu's Most Wanted," last season played a serial killer who ate his victims. Frankie Muniz, the young brainiac title character in "Malcolm in the Middle," portrayed a tortured graphic artist who took bloody comic-book-style revenge on his adversaries. And Cybill Shepherd ("Cybill," "Moonlighting") plays the mother of a serial killer in an upcoming episode.

Edward Allen Bernero, one of the drama's executive producers, said casting established actors against type makes the show's premise more effective. "It's hard to imagine Jason Alexander killing 12 people, but that goes a little bit of distance of what we're trying to show. A serial killer could be your next-door neighbor. It's the last person in the world you would think of."

Some guest stars have been surprised when approached by producers to play killers, said Bernero.

"The most common reaction is, 'Really? Me?' But then they really get into it because it's exciting for them to do something they don't usually get to do. And I'm never surprised at a comic actor who can reach that dark place."