Mario & Luigi: Undertale Mashup is a game that crosses over with Undertale, it is created by Pingy Animatronic.
When Mario & Luigi are roaming, they accidentally fell into the ground! So they must find their way back before it's too late!
- The Ruins
- New Home
- Bowser (Tutorial Fight)
- Papyrus (Who tries to capture Mario, Luigi, and Frisk but is befriended by the Trio at the end of the boss fight)
- Undyne the Undying
- Bowsriel Dreemurr (Final Boss, when Bowser is possessed by Asriel Dreemurr)
- Papyrus X
- Mettaton X
- Undyne the Undying X
- Jerry X
- Muffet X
- Kamek X
- Asgore X
- Photoshop Flowey (secret boss fight when finishing the Battle Ring medley)
Differences from other Mario & Luigi games
- Toriel replaces Toadsworth as the tutorial guide
- Badges are still replaced by Battle Cards
- Alphys gives bonus points to Mario, Luigi, and Frisk instead of Lakitu
- Bosses have different themes
- The game doesn't feature a Wiggler boss.
- Players can Flee Boss fights.