This bunny is earless. But why? According to the buzz on the Internet, it's because he was born near the site of the Fukushima Daiichi nuclear power plant meldown—the victim of radiation exposure in the womb. Theoretically, that could be true. But I'm not convinced. Specifically, before you let this bunny give freak you out, I think you need to demand two key pieces of evidence.
First, we don't actually know where this bunny came from. Everything I've seen on it is based on one video, and isn't particularly well sourced. Without that, it's impossible to know whether the bunny even comes from Japan, let alone the Fukushima area. It's also impossible to know whether this bunny was really born recently.
Second (and probably more important) earless bunnies aren't a particularly rare phenomenon. You don't even need a genetic mutation to get one. In fact, mother bunnies—especially those living with overcrowding, or other stressful conditions—are known to "over groom" newborns, biting their little ears down to nubs in the process. It's a common enough occurrence to spark debates on rabbit owner websites over whether or not earless baby bunnies should be killed. (And three years ago, Vincent the earless bunny—born nowhere near any recent nuclear meltdowns—became an Internet sensation on the strength of his cuteness alone.)
It boils down to this: Radiation exposure has health risks. Radiation can be a teratogen—something that can affect the physical development of a person or animal. But a weird-looking bunny in a video is not necessarily proof of a nuclear-related mutation in Japan. I'm not saying there's no way they could possibly be related. But, to start believing that, I'd first need proof that this bunny is from where he's supposed to be from, is the age he is supposed to be, and that he actually exited the womb earless. Until that exists, I think it's more likely that this bunny (wherever he's from) became earless the same way most earless bunnies do.