Judith Martin co-founded the Paper Bag Players in 1958. Now the troupe’s artistic director and playwright, she speaks easily of the early days of the children’s theater company, when she had to sweep up drug paraphernalia and shoo sleeping junkies off the stage before the matinees. Thankfully, she says, those days (in a little theater off Union Square) are gone. But Martin, a sprightly 87-year-old, decided it was now time to tackle another serious issue, albeit in front of an audience: bullying. In Pineapple Soup!, Kevin Richard Woodall, the physical comedian of the Bags, plays Rudy, the lead role in a musical sketch called “Big Bully.” When his friends turn on him, Rudy becomes an even bigger bully and threatens the young audience, saying, “I’ll beat you up one at a time. C’mon, I gotta hit somebody.” The violent solution goes wrong, lessons are taught, and Rudy, through the troupe’s clever musical silliness, learns to listen to the voice inside that says “don’t do it.” Surprisingly, Bag staff gave Martin a little grief about the segment, wanting her to make it less farcical and more hard-hitting. She stuck by her guns: “When the kids laugh at something, it gives them a kind of power, and they’re not overwhelmed by the image of the bully,” she said recently from the Lower East Side tenement studio that the Bags have occupied for the past 40 years. Just as the remarkably strong Tyvek paper used for costumes and scenery season after season holds up, so does Martin’s insight into the kid mind.