Screenshot: Unicode character #x1F600, 😀
Run M-x no-emoji-minor-mode to replace all emoji with :emoji-name: in the current buffer.
Run M-x global-no-emoji-minor-mode to replace all emoji with :emoji-name: in all buffers.
You can customize the no-emoji face to alter the appearance.
You can adapt the codepoint ranges in no-emoji-codepoint-ranges to customize which codepoints will be replaced.
This package sets buffer-display-table locally.