I recognised it straight away when it popped up this morning and thought "What the fuck, how could anything even trigger that?". There were no issues mentioning it for the longest time so we figured no way, it must be something besides npm.

I'd argue that 418 veers more towards "trivial" than it does "famous." Expecting knowledge of more than 400, 401, 403, 404, and maybe 412 is pushing it.

I didn't know 418 and I'm a web dev. Http status codes are a tiny part of my job

Not only that, but if you’re returning this status code you’re almost certainly doing something wrong or user hostile.

What if it really is a teapot? Not that farfetched with today's internet connected devices.

I still don't think returning a 418 (in the realm of client errors) is the correct code, even if it is a connected teapot which you're trying to identify!

I think the appropriate action would be a client sends an HTTP HEAD to the service, which responds 200 "TEAPOT".

There’s the EKG+, an internet connected smart kettle:

http://fellowproducts.com/shop/staggekg/

I have the plain EKG, and quite like it.

However, both are designed for pour-over coffee, so can’t correctly return 418.