I would laugh so hard if someone mananged to make that.
This isn't the first time it's been asked, I seem to remember trying to figure out if a mario ? block (a print cube) could have a different print on top.
My only guess at all is to have separate bricks, with 0 (or as close to 0 as possible) thickness (for height and width). Frankly, it would be pretty darn cool if someone managed to make that. It would probably be supported from the inside by a cube or something, but idk. Maybe that would work better if the underside had a 2x2 brick attatched as part of it, so there would be a plus-shaped support for them.
All this is just the random speculations of a noob who doesn't know what can't be done, so it's probably way off.