I did solve the level, but I don’t want to spoil completely,
So spoiler alerts below,
There are some guys to find, you can find them on certain levels. They’re not that many. If you don’t want to lose progress/replay, you can try incognito playing the game. I still wish there’s a level select to make checking other levels back easier.
And a tip, as long it’s reachable/you can check every single area, it’s likely there, and they do not appear on single sugarcube areas (or I dunno what the erasable cubes are called even then anyway.)