Coolboy Mario 40 in 1 is a multicart for the Famicom that contains various hacks of the Mario series. It will be presumably be available on AliExpress at an unannounced date.
Coolboy's official account on Tencent QQ was first used to announce this cartridge.
"we will make a new game card with 40 in 1. it will have many mario hack and be compatible with subor d99 8 bit tv game"
-Coolboy's Tencent QQ blog
The game listing is not known fully yet, but we have seen a screenshot of the first part of the menu. This is what it has:
SUPER MARIO - Most likely the very first Super Mario Bros. game
SUPER MARIO 2 JP - This is the Japanese "lost levels" game, presumably.
SUPER MARIO 3 - Most likely Super Mario Bros 3. What region it is is unknown, but it's probably the Japanese version.
DR MARIO - Most likely Dr. Mario, the puzzle game.
MARIO ADVENTURE (With a "NEW" Symbol) - It could be the infamous "Mario Adventure" ROM hack of Super Mario Bros. 3.
Nintendo of America posted on Twitter that Mario classics are available on the virtual console and there were great new Mario titles on the Wii U, citing that there was no need to ship a cartridge all the way from China.
"You can always download great classic Mario titles from the Wii U and 3DS eShop, and there's always great 2D Mario titles such as New Super Mario Bros. U to check out on the Wii U and 3DS consoles, with no need to ship a cartridge all the way from China!"
- Nintendo of America's Twitter
Nevertheless, fans are excited to see a new multicart from Coolboy announced officially, instead of being released without notice.