Some people have favorite numbers, and since character encodings are basically mappings from binary numbers to characters, I think it's pretty much equivalent to say I have a favorite character! U+200D ZERO WIDTH JOINER (ZWJ) is used to combine separate characters, usually in Indic and Arabic scripts. In my life as an English speaker and writer, it's used to make combinations of emoji, such as \ud83d\udc69+\u200d\u2764\ufe0f\u200d+\ud83d\udc69= \ud83d\udc69\u200d\u2764\ufe0f\u200d\ud83d\udc69. I'll talk about how and why this works, and how it might affect the text that users submit and you display.

(If the emoji in this abstract don't combine into one image on the right, try viewing on a recently updated smartphone.)