The 'Say it Again, Dexter' meme originates from the 1996 episode 'The Big Cheese' of the popular animated series Dexter's Laboratory. In this episode, Dexter tries to learn French via a sleep-study record, but the machine malfunctions, leaving him only able to say 'Omelette du fromage.' Surprisingly, the phrase makes him a sensation, culminating in a scene where a girl whispers 'Say it again, Dexter' into his ear. The meme is typically used to highlight how a specific, often nonsensical or nerdy phrase can be perceived as incredibly appealing or 'smooth' in a humorous context.