Mark Ritts, who played Lester the lab rat on the children's science series "Beakman's World" and also operated and voiced the puppet co-host Kino on the PBS children's show "Storytime," died of cancer Monday at his home in La Cañada Flintridge, Calif., said his wife, Teresa Parente. 
The son of puppeteers Paul and Mary Ritts - their Ritts Puppets was a popular act that often appeared on television beginning in the early 1950s - Mark Ritts began working with puppets as a teenager, when he assisted his parents on their television shows.
When he began work on "Beakman's World" in 1992, he thought he'd be operating a puppet named Lester the rat.
"He showed up in a white Panama hat and a leather shoulder bag, and we dropped a bomb on him: 'You're wearing a rat suit,' " recalled Paul Zaloom, who played the eccentric scientist Beakman, who responded to viewer questions about science and how things work from his idiosyncratic lab.
When the giant rat costume was brought in for Mr. Ritts to try on, Mr. Zaloom said, the arms had not yet been sewn on. "A rat suit with no arms: We took one look at it and said, 'That's perfect.' "
Instead of wearing a costume rat's head, the bearded Mr. Ritts wore a whisker-sprouting rat nose. And, said Mr. Zaloom, "we made sure the elastic that held the nose on was 100 percent visible."
"Beakman's World," which began in 1992 in syndication and on the Learning Channel, moved to CBS, where it ran from 1993 to 1998. It is still in worldwide syndication.
During the 1990s, Mr. Ritts also voiced and operated Kino, the 7-year-old boy puppet, on the PBS reading series "Storytime," for which he won a Los Angeles Emmy Award as the puppet co-host. Mr. Ritts also was one of the writers.
For Mr. Ritts, it was an opportunity to work with a long list of celebrities who read children's stories to the young viewers, including John Goodman, Tom Selleck, Ellen DeGeneres, John Ritter, Kirk Douglas, Little Richard and Kirsten Dunst.
He was born June 16, 1946, in West Chester, Pa., and grew up in Princeton, N.J. He earned a degree in English literature at Harvard University, where he also was active in theater.
Among other things, he later made short films for corporate clients, and produced public service announcements and live corporate shows. He also continued his sideline as a puppeteer on NBC's "The Pink Panther Show," PBS' "The Real Adventures of Sherlock Jones and Proctor Watson" and other TV shows.
More recently, Mr. Ritts and longtime collaborator Ted Field had been producing a series of boating videos, including "Cast Off for Catalina" and "Cast Off for Mexico."
You can leave condolences in the Guestbook at his official website