Input emojis in XFCE? – Ask Ubuntu

I’m puzzled:

I’m running Xubuntu 20.04.5 – and I swear I saw a 2y old kid accidentally spawn an emoji-input option in something like Mousepad. The emojis shown in a table were black/white font-ish, not colored bitmaps.

To be honest, I don’t recall which editor exactly – but I cannot find out how that kid has done that. I can’t find any information about a keyboard shortcut that would do that.

I’m very sure it wasn’t any web-browser. 😉

Does anyone have an idea about an emoji-input-option like that, installed by default?
Thanks a lot.