I'll be back in a jiffy

It's a common expression; "He'll be here in a jiffy,", "I'll be back in a jiffy," Most people shrug it off as just another expression, such as "Back in a sec," but in fact, a jiffy is actually a true unit of time--1/100th of a second. So while not exactly doable, the old expression does have some backing to it, just as a google is actually a number-10^100.