Keeping a comedy venue afloat for 23 years is no joke. Michael and Cheryl Alfano took over ownership of The Comedy Catch on Brainerd Road in 1987, two years after comedians Ken Sons and Les McCurdy opened the club atop the Holiday Inn downtown. In August, the Alfanos will mark the club’s 25th anniversary with two weekends of special-engagement acts: David Alan Grier and Cledus T. Judd.