Self-fiction and play, double entendre and wit, slippery authorship and off-site-ness are the underpinnings of Allen Ruppersberg’s oeuvre. The Conceptual artist’s retrospective at the Walker Art Center, “Intellectual Property 1968–2018,” foregrounded his persistent fascination with the American vernacular—its humor, horror, literature, and pop culture—unfurled through a thematic and chronological sequence of galleries. EACH WORK IS ONE OF A KIND, as Ruppersberg once wrote in “Fifty Helpful Hints on the Art of the Everyday,” 1985. The show strung experiments into a narrative, bracketed by