Mario, Luigi, & The All-Stars: Partners in Time is a crossover fan fiction and the sequel to Paper Mario All-Stars.
After the events in Paper Mario All-Stars, the Mario Bros. and the Mushroom Kingdom are enjoying a time of peace as Prof. E. Gadd reveals his latest invention: a time machine. Princess Peach uses it to see the Mushroom Kingdom of old, but when she is kidnapped by a group of aliens known as the Shroobs and the time machine causes a rip in the space-time continuum, heroes new and old team up to save the kingdom and all of history. But, there are many surprises along the way...
The following characters that will be part of this story are:
- Mario - Mario, Luigi, Baby Mario, Baby Luigi
- Sonic the Hedgehog - Sonic, Tails, Knuckles, Amy Rose, Shadow, E-123 Omega, Silver, Jet, Metal Sonic
- Pokémon - Ash, May, Max, Brock, Pikachu, Team Rocket
- Kingdom Hearts - Roxas, Axel, Xion
- One Piece - Luffy, Zoro, Nami, Usopp, Sanji, Chopper, Nico Robin, Franky
- Swat Kats - Razor, T-Bone
- MegaMan - X, Zero
- Inuyasha - Kagome, Inuyasha
- TMNT - Leonardo, Donatello, Raphael, Michelangelo