pull the other one used to express a suspicion that you are being deceived or teased. British informal
☞ A fuller form of this expression is pull the other one, it's got bells on. It extends the idea of pulling someone's leg (see above).
2004Andrea LevySmall Island 'The Japs have surrendered,' Maxi informed me. 'Pull the other one,' I told him. 'Everyone knows Japs don't surrender.'