Gregory's Server
If you use a "woman-facepalming" or "man-facepalming" #emoji in #Mastodon web interface, and try to delete it via backspace, it will turn into a "person facepalming" (which for some reason is missing on both of my instances).
This is because both these emojis are a ZWJ (Zero Width Joiner) sequences:
🤦♀️ is actually 🤦 (U+1F926) + ZWJ (U+200D) + ♀️ (U+2640 U+FE0F).
🤦♂️ is actually 🤦 (U+1F926) + ZWJ (U+200D) + ♂️ (U+2642 U+FE0F).
Note that U+2640 is plain ♀ ("Female Sign"), while U+2642 is plain ♂ ("Male Sign"). U+FE0F is "Variation Selector-16" which turns a "plain" #Unicode character into "emoji presentation" (though apparently Mastodon implicitly turns the former into the latter after publishing).
You can also combine them with skin tone modifiers. Curious enough, these don't use ZWJ (I guess because they're modifiers by design):
🤦🏿 is 🤦 (U+1F926) + 🏿 (U+1F3FF, "Modifier Fitzpatrick Type-6")
@mgorny Also if you pick family emoji and try to backspace on it, it will delete family members one by one.