Imajin, Mama, Papa, and Lina are the four playable main characters of the japanese game Yume Kōjō: Doki Doki Panic, a game that was later released outside of Japan in an altered format under the name Super Mario Bros. 2, since the original Japanese Super Mario Bros. sequel, Super Mario Bros.: The Lost Levels, was deemed too similar to the original and too difficult for overseas players.
The game takes place inside a book. The book's story tells of the land of Muu (which name was changed to Subcon for Super Mario Bros. 2), where the quality of dreams determined the quality of the weather the next day. Because of this, the Muu citizens invented a dream machine so they could always have good dreams. One day, an evil toad named Mamu (whose name was changed to Wart for Super Mario Bros. 2) invaded the land and twisted the dream machine into a nightmare machine. However, the Muu people learned of his weakness to vegetables and used them to defeat him.
The book had found its way into an Arabian family. Their pet monkey, Rusa, gives the book to twins Poki and Piki. However, the twins quarrel and end up ripping out the last page of the book, causing its ending to be erased. Mamu, freed, reaches through the pages and grabs the twins, pulling them into the book. Rusa gets the twins' parents, Mama and Papa, their brother, Imajin, and Imajin's girlfriend, Lina, and they enter the book to both rescue them and save the Muu citizens by defeating Mamu and his army of monsters.
- Imajin is the balanced character. While Mario replaces him, Imajin's balance in all areas has since become a staple of Mario's in certain games.
- Mama has the ability to jump higher and lightly hover at the top of her jumps. Luigi takes her place as he had already had higher jumps than Mario in Super Mario Bros.: The Lost Levels. However, Luigi can jump slightly higher than Mama. Like his brother's balanced stats, his higher jumps has stayed in the Mario franchise.
- Lina can hover, although she is low in speed and strength. Princess Peach replaces her. As a result of the license with Fuji Television expiring, Peach inherited Lina's floating capability and it would be later seen in the Super Smash Bros. series starting with Super Smash Bros. Melee (her first appearance in the series), Super Mario 3D World and Super Mario Run (with the addition of slowly descending in mid-air).
- Papa is the strongest character in the game and can run the fastest, but he is not very good at jumping. While a Toad takes his place, in future video games (other than indirect references in Wario's Woods and Mario Superstar Baseball), Toad rarely has Papa's stats. However, Toad regains these properties in Super Mario 3D World and Super Mario Run, where he is the fastest character and a poor jumper.