Scratch one's back هوای کسی را داشتن
If you lend me the money I needed , I'll help you paint your house . you scratch my back and I'll scratch yours !
Pull someone's leg کسی را دست انداختن / سر به سر کسی گذاشتن
Come on , don't get mad ; I'm just pulling your leg
Are you pulling my leg؟ منو دست انداختی ؟