Jerry Seinfeld will perform his first televised stand-up routine in three years on CBS's The Late Show with David Letterman Wednesday. The last time the funnyman did his shtick on TV was for his 1998 HBO special I'm Telling You for the Last Time. This will mark Seinfeld's 42nd appearance on Letterman's show; he most recently sung "Sixteen Going on Seventeen" from The Sound of Music with his ex-Seinfeld co-star Julia Louis-Dreyfus.