Are there any Terminal commands that would be interesting for a young child? I am beginning to teach my 4-year-old daughter that she can do more on a computer than watch cartoons on Netflix. I want her to know that she can type things on the keyboard and make the computer do stuff.

For example, I opened Terminal, turned the font size way up, and showed her that if she typed say emily, the computer would speak her name. She was elated with that and immediately wanted to make the computer say all her friends' names, too.

She does not yet have the motor skills to reliably operate a touchpad or mouse, but she knows her letters and can type just fine.

Are there any other Terminal commands, besides say, that a young child might find interesting?
If you have an older computer with "X" pre-installed, xeyes is mildly entertaining.  

But, you could also create an alias or a shell script that does just about anything, using applescript, etc.