ON THEIR MARKS: Runner Runner, the first band signed to David Letterman’s Worldwide Pants label Clear Entertainment/C.E. Music through Jack Ponti’s MRV and EMI Music’s Capitol Records, will perform their debut single, “So Obvious,” on the Late Show With David Letterman on Sep. 29. Fans can enter the “Run Away With Runner Runner to NYC” contest now through Sep. 15 here to win a trip to NYC to see the performance. The band’s self-titled debut comes out Dec. 7, a day that has even more reason to live in infamy. The “So Obvious” video has been added to MTV Hits, mtvU and Teen Nick and has been raking up thousands of You Tube views a day. Check it below. (9/7p)