Karlen reprised the role of "Willie Loomis" for a series of Dark Shadows audio dramas produced by Big Finish Productions.

Karlen was born May 28, 1933, in Brooklyn,[1] the son of Helen Agnes (née Balondowicz) and Adam Marion Karlewicz.

It was Karlen's pivotal character of Willie Loomis who released vampire Barnabas Collins from his coffin, setting off the events of the series.

Karlen won an Emmy Award for his portrayal of Harvey Lacey in 1986; he received 2 further nominations, in 1985 and 1987.

Karlen died from heart failure in Burbank, California on January 22, 2020, at age 86.