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Leo the Little Leaguer, or in this case just Leo, was a single panel comic created by Walt Lardner that ran for a fairly short time, though it did get picked up by a few high profile newspapers. It was, as its name suggests, about a kid who plays Little League baseball, and generally had jokes revolving around that and other sports. From what I could find, it started in March of 1966, and most client newspapers didn't carry it past October, but at least one stuck it out until the end of the year. Lardner's art style was delightful, and the gags weren't too bad, so it's a shame that it didn't last longer than it did.