    Sentence 1: What day of the week did Shark Tank debut  on?    Sentence 2: Shark Tank (based on the Dragon's Den  reality format) also became a midseason sleeper hit on  Sundays in the spring of 2010; the following season, it  became the tentpole of the network's Friday night  schedule, gradually helping make ABC a strong  competitor (after being paired with 20/20 and  beginning with the 2012-13 season, the Tim Allen sitcom  Last Man Standing) against CBS' tong-dominant  drama/reality lineup on that night for the first time  since the "TGIF" lineup ended in 2000.