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Wednesday’s episode of “Chicago Hope” joins a small but unheralded group of TV comedies or dramas that went on a one-time musical bender.

“Northern Exposure” — In “Old Tree,” which aired May 1993, Shelly Tambo (Cynthia Geary) has a strange reaction to being pregnant with Holling Vincouer’s (John Cullum) daughter: She carries on “musical conversations” with everyone (“I woke up this morning/without any warning/A song were there in my bod”). The episode ended with Holling tenderly joining a fretful Shelly in song, telling her “sing or talk, I’m by your side.”

“Quantum Leap” — This NBC time-travel series slyly sneaked a musical into the plot line of “A Single Drop of Rain (Sept. 7, 1953),” an episode that aired November 1991. Wayward scientist Sam Beckett (Scott Bakula) transported into the body of Billy Beaumont, a “purveyor of precipitation.” In short, a rainmaker trying to work wonders in a small town in the grips of a devastating drought. The episode was a thinly veiled homage to “The Music Man,” with Bakula, a veteran Broadway singer and dancer, smoothly essaying a Harold Hill-type role.

“The Simpsons” — The Fox animated series has spoofed almost everything else under the sun, so why not a popular musical movie? When Marge Simpson suffers from stress-related hair loss in an episode this past February, the family decides to bring in a nanny named “Shary Bobbins,” who just happens to float through the skies of Springfield with her umbrella. Takeoffs of “Mary Poppins” classics included “Minimum Wage Nanny,” “A Boozehound Named Barney” and “Cut Every Corner.” The episode’s title? “Simpsoncalifragilisticexpiala-d’oh-cious.”