Super Mario Advance 4 is an enhanced remake of the NES game Super Mario Brothers 3, released for the GBA. The NES original, and its SNES remake which this shares something of a codebase with, is often considered one of the best 2d Mario games. For its GBA release some extra levels and abilities were added via the "ereader" peripheral, these extras making it something of a definitive version of the title. Not all of them made it out of Japan, and as Europe never got the ereader peripheral they never made it there. There was a version released for a virtual console later on that included said levels as a Nintendo made ROM hack, however as distributing said extras as a patch is legally dubious we get to stick to the more traditional ways. In this case one of our newer members, Renegade_X135, dropped in to share their collection of newly remade dot codes, translations of the levels (the North American version not featuring a Japanese font made the level names display as jumbled nonsense), the tools they used to make it, some discussion of the effects various things have, and a level which apparently was corrupt in the older releases.
With this then no longer should you have to find said patch (which also has issues with older hacks), mess around with partially corrupt (and possibly already completed) saves or suffer other such annoyances.
You may also like to grab a copy of the palette restoration hack
as it is one of the games that suffers a brightened palette (many earlier titles and ports had this to help deal with the unlit screen on the original GBA).
Release thread (includes downloads)