Yeah here's what he said:
"I gotta tell you, we had a LOT of fun making the two GBC games, best time in my career (followed by the worst time in my career with the GBA Azkaban...) The publisher didn't really pay attention to our games, they were only concerned with the console and GBA versions, so we were able to do almost whatever we wanted without interference. Every once in a while we'd show them progress, they'd say "We didn't think the GBC could do this, keep up the good work". Because of that, the GBC games were closer to the books than any of the other ports, where they weren't allowed to put it in if it wasn't in the movies.
We used a bunch of tricks in Chamber of Secrets, and maxed out the largest GBC cart size, with only a few bytes to spare. The most-used trick was to do things while the screen is being drawn - load a whole new set of color palettes partway down the screen to get hundreds of colors per screen, scroll the screen at different rates on different scanlines, change the memory address of the backgrounds so we could flicker a ghostly background in front of the normal one (used a lot in card attacks). We also had a lot of background animations done by manipulating the palette, known as "palette cycling".
We were micromanaged to death by the publisher on that one [Prisoner of Azkaban]. They specifically asked for the GBC Potter team to make that game, and we designed our dream game, taking everything we learned from Chamber of Secrets and amping it way up, taking full advantage of the powerful new hardware. To be honest, we over-designed it, to be sure, but still, without interference we could have made a really kick-ass game. But the publisher didn't trust us to make quality GBA art, seeing as we had come from GBC development. To make a long story short, halfway through production they made us throwaway all the existing background art, replacing it with a new style they came up with, and because the background art changed, we had to change our sprite art to match, and now all the scripting had to be redone, since backgrounds and characters were different sizes/shapes from before. With only half the time to now make a full game, we had to cut many, many features, and to release it as a decent game we had to work crunch mode for the rest of the project, including weekends and holidays, while the publisher had reps in our office micromanaging it all. Not fun."
https://www./threads/rttp-harry-potter-game-boy-rpgs.743011/#post-95347786