Sam & Cat é um spinoff de iCarly , então sim, eles acontecem no mesmo mundo.
Da página da Wikipédia:
Sam & Cat is an American teen sitcom that originally aired from June 8, 2013, to July 17, 2014, on Nickelodeon. It is a crossover spin-off/sequel of both iCarly and Victorious. It stars Jennette McCurdy as Sam Puckett and Ariana Grande as Cat Valentine.