oneko ("cat" in Japanese) is a classic X11 novelty: a small animated cat (or other character) chases your mouse cursor around the screen while you work.
sudo dnf install oneko # or apt-get install oneko (X11 only; does not run under pure Wayland)
oneko # default cat
oneko -tora # a tiger-striped cat variant
oneko -dog # a dog instead, chasing a bone
oneko -bitmap3 # alternate sprite set, if installed
Kill it with pkill oneko or by closing its window if it has one. It requires an X11 display; it will not run on a pure Wayland session without XWayland support for the specific drawing calls it uses.