My blog post about my Red Hat shell prompt proved very popular, although some people tried my instructions and couldn't get it to work, so here's some further information.

The unicode code-point I am using is "🎩", U+1F3A9 TOP HAT. My Terminal font of choice is Noto Mono Regular which does not contain a glyph for that code-point. Therefore the font system my Terminal uses (pango) is pulling it from another font. In my case, it's using OverPass Mono, an open source font created for Red Hat branding. The TOP HAT glyph in OverPass Mono is a Fedora. This is a nice little easter egg included by the font authors. (There's at least one other easter egg in the font, by the way!)

It's pure chance that my font system chose OverPass Mono to pull that glyph.

The simplest way to get this to work is (probably) to download and install "OverPass Mono" and set your Terminal font to it for all characters. Alternatively you may need to look at configuring Pango (or whatever font system you are using).

If your Terminal and font system support multicolour emojis, then the above alone may not work for you. Some of my colleagues got a nasty surprise when upgrading their systems: their red hats turned blue. It's possible to add a trailing Unicode modifying code-point that instructs the font system to not render the prior glyph using multicolour emojis. This reportedly fixes it:

combiner="$(perl -CS -e 'print "\N{VARIATION SELECTOR-15}"')"
# ^ alternatively, "$(printf '\xef\xb8\x8e')"
export PS1="\[\e[31m\]${hat}${combiner}\[\e[0m\]"

(Thanks ilmari for the perl trick)