And now, a (very old) hidden message. While examining a Spanish MSX game from 1990 called "Power Magic" I found something interesting.

The loading screen looks "normal" (typical pixel-art originally made on a ZX Spectrum and ported to the MSX).

However, if you remove the colour attribute and show the pixels only, there is a hidden message dedicated to publisher Dinamic.

For non-Spanish speakers, the translated text reads: "BASTARD DINAMIC. THEY DO NOT PAY THEIR FREELANCERS".

A bit late..

@msxwiki
Images show that pixelart loading screen, with and without color attribute. They a have a wizard and a warrior with a sword fighting. It says "DINAMIC CABRONES. NO PAGAN A SUS FREELANCE JB"
@msxwiki haha, I remember reading about this on the book "Ocho Quilates"
@msxwiki
I should see this in original ZX-Spectrum version. There, color attribute is applied after pixel on/pixel off, so in a non-turbo load (e.g. via a pirating device) the text could be revealed.
@msxwiki They (or their counterparts in the UK) seemed to skimp on translation as well. I remember some box copy from a Dinamic game where they left the text around some sci-fi neologisms untranslated (IIRC, “Garklas clonicos”, which should have been translated to “clone Garklas”), presumably as they were doing it in a hurry.