A guy goes into a costume shop. He says, "I'm going to a costume party and I want to go as Adam."

 The girl brings out a fig leaf. He says, "Not big enough." 

She brings out a bigger one. He says, "Still not big enough." 

She brings out a huge fig leaf. He says, "Still not big enough." 

She says, "Listen, Bucko, why don't you just throw it over your shoulder and go as a gasoline pump?