But those were concepts, not individuals. There were four Rin Tin Tins over the years, and obviously the Lassie of the 1943 movie "Lassie Come Home" wasn't the Lassie of the 2005 eponymous movie.

Skippy was different.

Like Harrison Ford playing Indiana Jones and Han Solo, Skippy played characters. You might know him from his most famous role: Asta.

He was a wire fox terrier, born in 1931 He made his first appearance a year later in a circus comedy called "The Half-Naked Truth." But don't look for him in the opening credits. Character actors, whether two- or four-legged, never got much notice.

His breakthrough came in 1934's "The Thin Man," in which he played the smart, personable dog of Nick and Nora Charles, the smart, personable alcoholic crime-solvers. The movie was a hit, and so was the clever dog.

In between "Thin Man" movies, Skippy worked with some guy named Cary Grant in "The Awful Truth" (1937). Grant and Hepburn's classic "Bringing Up Baby" (1938) also featured Skippy as the naughty dog who steals a dinosaur bone. And he was in the 1937 "Topper" movie, as well, which suggests that people had come to expect that a sophisticated comedy would include a fox terrier.

During his Hollywood years, he did have a run-in with a diva: He bit Myrna Loy between scenes on their first "Thin Man" film. That, however, didn't keep her from working with him again. Or vice versa.

Guiding Skippy (and subsequent Astas through their careers) were the most acclaimed dog trainers in Hollywood, actress Gale Henry and her husband, MGM FX man Henry East.

Among their assistants were Rudd Weatherwax, who'd go on to produce the nation's supply of Lassies, and Frank Inn, who trained Higgins, an adorable mutt who played Benji in the movies of the same name, and the unnamed pooch who hung around the hotel in TV's "Petticoat Junction."

Henry East said he knew Skippy was destined for stardom when he saw him in a pet shop window.

All the other pups were sleeping, but Skippy was pressed up against the glass, eager to see everything. East took him home and put a bone in an unused movie camera. For the rest of his career, Skippy looked into the camera to see if it might contain a treat. It didn't, but what the camera saw was a treat for the audience.

Skippy retired in 1941. That may be a euphemism for "died."

Unlike the first Rin Tin Tin, whose 1932 death was so newsworthy that the radio broke into regular programming to announce his passing, Skippy just faded away, replaced by other terriers that may or may not have been his descendants.

There were six "Thin Man" movies, but Skippy appeared in only three or four. His official imdb.com biography says his great-grandpuppy played Asta in the 1957 "Thin Man" TV show.

His descendants may be alive today. Even if they aren't, there's a little Asta in all fox terriers.

James Lileks • 612-673-7858 • @Lileks