What’s the name of that early anime image from the 2000s where you highlight it and it reveals a hidden drawing? And how can I do that to my drawings?

There was this post that was trending on Twitter a couple months ago about someone searching for the exact same thing. I believe it was a picture of an anime girl with the early 2000s style and when you hover the mouse over it to highlight it, it reveals another secret drawing due to the blue highlight of the mouse. I was wondering how exactly can I do something just like that with my art? I would like to try that technique.