Steve Martin is almost 20 years older than Minnesota Gov. Tim Walz, but after Vice President Kamala Harris named Walz as her running mate Tuesday, plenty of people pointed out the resemblance between the two men and urged Martin to play Walz on Saturday Night Live. Rolling Stone calls the resemblance “uncanny.” Martin acknowledged the interest, quipping on Threads: “I just learned that Tim Walz wants to go on the road with Marty Short.” But when SNL producer Lorne Michaels called on Wednesday morning, it was an offer Martin could refuse. “I said: ‘Lorne, I’m not an impressionist. You need some…