Poker face
I used to have the best poker face. I could pull a fast one on my grandmother so easily. We're smart people, but also a tad gullible. I could do the best April Fool's pranks, or even the odd end of the school year "I've failed" joke, right before passing her the report card full of As and Bs. I pulled the "I'm pregnant" trick one year, but that's no longer possible given that I'm by-choice post surgery sterile; nor do I think she'd buy the immaculate conception bit, no matter how much Catholicism she practices. I've got dry wit.