Fonejacker was a British television comedy built around prank calls, with its caller using disguised voices and invented characters to catch unsuspecting people in strange, improvised conversations. The show became known for quotable lines that worked outside their original calls, and short clips have continued to circulate among fans and editors long after broadcast. Stretch a canvas fits that pattern: the exact call is not widely documented, but the phrase survives as a compact, reusable joke about art, selling and deadpan confidence.