There's something fascinating about how languages capture human vanity differently. The most direct translation would be 'self-conceit' or 'narcissism', but those feel too clinical. In casual conversations, I've heard 'big-headed' used playfully among friends - like when someone brags about their cooking skills but burns the toast.
Interestingly, British English tends toward 'up themselves' while Americans might say 'full of themselves'. Pop culture gives us great examples too - think Gaston from 'Beauty and the Beast' belting 'I'm especially good at expectorating!' That scene perfectly illustrates how self-absorption can be both ridiculous and entertaining.