Trammell Hudson in 2009 reverse engineered the firmware of the Canon EOS 5D Mark II because he was frustrated with some of the limitations in the camera's firmware when making short films. That little hack turned into Magic Lantern. On his website [1] you'll find a screenshot [2] of his first success: adding three extra vanity letters to the firmware version number.
He states: "Re-writing strings is a good easy technique for figuring out if you have 'won' and your code is running on the system."
[1] https://trmm.net/Taking_things_apart#Extending [2] https://www.flickr.com/photos/osr/16412008471/lightbox/