It's Mr. L, the one and only! And his trusty Brobot L-Type, who shoots missiles!
This theme was inspired by an official Super Paper Mario wallpaper from the Japanese Nintendo website. The top screen image anyway, the rest is improvised.
PM:TTYD Remake sprites have been used to make the details on the folder, the base folder and icon frames have been taken from the Rhythm Heaven Badge Arcade theme.

Comes with custom sounds!

Credits:
Mr. L, the Brobot L-Type and Super Paper Mario logo artworks sourced from the Super Mario Wiki
SMB Luigi sprites ripped by "SuperJustinBros" on The Spriters Resource
Mr. L and PM:TTYD Remake Kammy Koopa sprites ripped by "fawfulthegreat64" on The Spriters Resource
PM:TTYD Remake Luigi sprites ripped by "DogToon64" on The Spriters Resource
PM:TTYD Remake Pennington sprites ripped by "geometricentric" on The Spriters Resource
Rhythm Heaven Nintendo Badge Arcade 3DS theme ripped by "JacintaB2022" on The Spriters Resource

Super Paper Mario sound effects ripped by "fawfulthegreat64" on The Sounds Resource

Background music taken from the "The Year of Luigi Sound Selection" by Nintendo

Brobot L-Type Battle [Super Paper Mario] - Naoko Mitome, Chika Sekigawa