Socks have a bad reputation as a gift and they earned it. A plain five-pack communicates nothing except that shopping occurred. But that's a failure of specificity, not a failure of socks.
The rule that makes this work
Buy for the obsession, not the occasion. The gift lands when it proves you were paying attention. Frog socks for the person who has mentioned frogs three times. Pickle socks for the colleague with the pickle thing. The sock is almost irrelevant — what you're actually giving is evidence that you listened.
So search for the person, not the category. Don't search "funny socks"; search the specific animal, food, hobby or running joke. The catalog goes deep enough that this nearly always works.
That's the frog version of this principle — subtle enough to wear anywhere, specific enough that the recipient knows exactly why you bought it.
The work-safe format
If you're buying for a colleague, the safest funny sock puts its text on the sole. The joke exists, but only when they choose to reveal it, which is a very different social contract from a slogan across the ankle.
What backfires
Face socks of the recipient. Brilliant for someone with an established sense of humour about themselves. Genuinely uncomfortable for anyone else. The pet version is much safer and usually funnier.
Anything sweary for a colleague. Even mild profanity changes meaning when it comes from someone you work with.
Body-related jokes. A surprising amount of novelty sockwear makes jokes about the wearer. Read the design twice before giving it to anyone you aren't close to.
For children, or adults who are basically children
The 3D category — spikes, ears, tails — works on a six-year-old and a forty-year-old equally well, which makes it unusually versatile. It is also the category most likely to disappoint if it's badly made, so favour pairs with real review counts.
Buying for several people at once
Build a drawer. It holds socks from different shops in a single list, shows a running total, and gives you one checkout per brand — so you can buy four gifts from four independent stores in one sitting without keeping four tabs open.
You can also share a finished drawer as a link, which makes it a decent wishlist: assemble what you want and send the page to whoever asked.
Timing
Seasonal designs, Christmas especially, are short production runs from small brands. They sell out in late November and do not get restocked. Assemble holiday gifts in October while the whole catalog is still there.
For everything else stock is reasonably stable, but the strangest pairs come from the smallest operations and can vanish without warning. If you find the exact right thing, buy it then.