mccI would like to suggest you watch the first three seconds of this video
YouTube
Luigi 
@mcc this was as much interesting as reading Fabien Sanglar's books on Wolf3D and Doom. Thank you for that
@luigirenna If you liked this you may also like the "Displaced Gamers" series.
In these videos the vlogger disassembles various NES games that re known to be buggy, and attempts to find and fix the bugs.
His videos on Teenage Mutant Ninja Turtles and Jekyll and Hyde (he did *two* on this game— there's enough strangeness in this game's code for two videos!) are particularly interesting.
The Wacky Frame Rate and Game Engine of Dr. Jekyll and Mr. Hyde (NES) - Behind the Code: Leveled Up
@mcc thank you! I will definitely check them out.
In return, this is something I read years ago and left me amazed.
https://gamehistory.org/aladdin-source-code/
And this is one of the most mind blowing things I have ever seen: code injection in SMW
Digging for treasure in Aladdin's source code | Video Game History Foundation
When it was released back in 1993, Disney’s Aladdin for the Sega Genesis (or Mega Drive, depending on which side of the pond you lived on through the early 90’s) was really a visually striking game. Powered by what eventually became known as “Digicel” technology, along with a solid selection of middleware and some impressive…