I've noticed that the size of a request often has almost nothing to do with the amount of work behind it.

Something like "just change this part of checkout" can end up touching shipping rules, coupons, taxes, payment gateways, order status, emails, caching, and a couple of plugins that all expect the original flow.

Meanwhile, a page that looks like a much bigger job can sometimes be straightforward.

Over time I've become much more careful when someone describes a WordPress change as "small."

What's the most deceptively simple request you've worked on that turned into a much bigger technical problem?