That happened to me while I was flashing linux with rufus.
Reminded me of the good old dial-up days with a Diamond 56 kbps modem!
open a terminal and type
or copy and paste
sudo apt install sl
hit enter (password required) then hit enter again
then just type sl and hit enter
i shouldn't do this should i. Is that the joke?
Kudos to you for not blindly installing that! 
A little more context would've been nice, but it's completely harmless. All it does it show an ASCII animation of a steam locomotive on the terminal.
Good call zenzen, I should have provided some info as to what the command actually does.
My apologies.
@qwert as anyone else is absolutely right to be cautious.
No worries! It's just not to scare people off that may already be way of unknown commands.
Another cool one is cmatrix to make the terminal look like The Matrix movies.
I'm getting a bit cheesed off with my dual boot errors.
Tried again and it's end of story.
I used to love that windows error video in the credits of The IT Crowd!
Most stupid linux distributions.
https://www.instalki.pl/news/software/najgorsze-i-najdziwniejsze-dystrybucje-linuksa-ktorych-linuksow-unikac/
Provided it has a compatible sbat shim! 