I don't own a pair of superman underwear, but I think I want to. I've seen these briefs on many gorgeous bodies on the internet, and they always inspire two simultaneous, somewhat paradoxical responses in me: laughter and arousal.
The arousal of seeing just about any exposed flesh on Seth Kuhlmann likely requires no further explanation. "Hot body" and "nothing but underwear" is sufficient to catch my eye and hold my attention. But Superman's "S" printed across the crotch of a gorgeous hunk's underoos is somehow even sexier, and not in small part because of the sense of humor it implies.
Of course, there are likely some muscle studs who'd don superman underwear without a sense of irony or humor. While these fine gentleman are likely delightful to watch in still frame, a man without a sense of humor (or anyone who takes himself too seriously), drops in sex appeal by a factor of 10 in my reckoning. Superman underwear as a means of promoting literal and sincere comparisons to the literary man-of-steel miss the full potential of this gear, as far as I'm concerned.
Superman underwear is silly. Sexy, yes, but also silly. Wearing them suggests that those who sport them can embrace silliness. They can stick their tongue in their cheek. They understand the provocative allure of a little self-deprecation that only heightens by contrast the hardcore sexiness of a witty, smart hunk who loves his body.
While I don't own a pair of superman underwear, I aspire to be the type of man who could pull them off. I aspire to love my body (daily work, but mostly there), and to wield both wit and smarts enough to recognize how sexy a little self-deprecation and a lot of humor can go.