Hide a message in an emoji

Pretty interesting trickery here, encoding a secret message in an emoji that you automatically get when you copy/paste it from Paul Butler.

Most unicode characters do not have variations associated with them. Since unicode is an evolving standard and aims to be future-compatible, variation selectors are supposed to be preserved during transformations, even if their meaning is not known by the code handling them. So the codepoint U+0067 (“g”) followed by U+FE01 (VS-2) renders as a lowercase “g”, exactly the same as U+0067 alone. But if you copy and paste it, the variation selector will tag along with it.

So you slap on a bunch of “variations” to a character that doesn’t support them (the secret message) and then pluck them off if you happen to know they are there. Sneaky sneaky.