Of my print dictionaries, only Oxford (by Ya’acov Levy) acknowledges the show-biz meaning of keta, calling it a performer’s “number.”  Viewing life as a cabaret, we may ask when someone behaves strangely “What is his keta?” — that is to say, his item on the program.  His routine, his gag, his schtick, his spot, his bit, his piece, his act, his stunt, his stuff, his trick.