Kids with knifes edged bosses in disguise last night as the series premiere of Fox’s Masterchef Jr. (1.6/6 in adults 18-49) won the 8 PM hour, squeaking past the season premiere of CBS’ Undercover Boss (1.5/6). Masterchef Jr. dwarfed the fall premiere of Fox’s Kitchen Nightmares in the slot in October (0.9/3), while Boss was down 21% from its November debut last season. In its Friday premiere, Hawaii Five-0 did a 1.5/6, down 17% from its season opener last night in the Monday 10 PM slot. The drop was far more modest than that for the previous procedural CBS relocated to the Friday 9 PM slot, CSI: NY, which lost 50% in 18-49 year-to-year in the move. And in total viewers, CBS’ main currency on Friday, Hawaii (9.4 million) actually was up 18% from last fall’s opener, while CSI: NY dropped 31%. Blue Bloods (1.7/6) was up 13% from last season’s premiere when the cop drama was hurt by a weaker lead-in, Made In Jersey (1.2). The Tom Selleck drama was once again the biggest draw on the night with 11.4 million viewers. The Friday top honors in adults 18-49 went to ABC’s Shark Tank (1.9/6) for a second straight week. The reality series actually ticked up by a tenth from its season premiere last Friday. But the bump was no thanks to a better lead-in as ABC’s 8-9 PM comedies tumbled from their soft openings last week — Last Man Standing (1.2/5, down 20%), The Neighbors (1.0/4, down 17%). That put a dent in ABC’s average and the network lost the top spot for the night to the other network that offered all-originals, CBS (1.6/5, 9.6 million) Among the newsmagazines, 20/20 (1.3) was flat, while Dateline (also 1.3) was up 11%.