Disney's The Little Mermaid is a 1991 video game was developed by Capcom for the Nintendo Entertainment System and Game Boy. It is a single player side-scrolling action game where the player controls Ariel on a quest to defeat Ursula.
Ariel has already met Prince Eric, and they plan to wed, but Ursula has taken control of the ocean. So Ariel (after explaining what's going on to Eric) becomes a mermaid once more and sets off to rescue the sea.
The game takes place from a side view and Ariel (swimming most of the time, but hopping around on the land occasionally) can shoot bubbles to trap her foes and can then throw them at each other. She can also dig through sand to find treasure and pick up sea shells to break chests open with. The treasure she finds in the sand is usually just bonus points, but the treasure you find in chests will increase your bubble's power and range. The gameplay is similar to other Capcom games such as Chip 'n Dale Rescue Rangers and DuckTales in that Ariel shoots air bubbles from her tail that when they hit certain enemies, can be picked up and thrown at other enemies or bosses. Ariel can also collect icons scattered throughout the levels to restore health, gain extra lives, or increase the range/power of her air bubbles.
There are some differences between the NES and the Game Boy versions. When a stage begins, Ariel descends from the top of the screen to the recommended starting point in the NES version, but just starts out in the recommended position in the Game Boy version. The featured sound effects are different in both versions. The start of the stage's BGM can be heard only once in the NES version; although the whole BGM can be repeated in the Game Boy version. The stage backgrounds were more restricted in the Game Boy version than in the NES version. When you lose a heart, the heart turns into a heart frame in the NES version, but disappears in the Game Boy version. The key scales of the Boss BGM are different in both versions. The BGM speed in the NES version is much faster than in the Game Boy version.
- The third level, Sea of Ice is the least canon to the film, as ice never appeared in the film; however that level appears to be a foreshadowing reference to the later film, The Little Mermaid II: Return to the Sea where Ursula's sister Morgana lives in an ice cave and has once trapped Ariel's daughter Melody and Flounder via a wall of ice.
- The walrus and the soldierfish (the bosses of Sea of Ice and Undersea Volcano, respectively) are not canon to the film. However, a walrus named Dash appears in The Little Mermaid II: Return to the Sea, but has only a few inches of tusks while the walrus in this game has full-length tusks.
- The layout of the fifth stage, Ursula's Castle is much different than the film. It is much larger and has doorways that resemble the face of a snake, and Ariel must travel up many stories to encounter Ursula (the boss). The lair in the film has only one story, and the distance from the entryway to the main hall is very short. Also, the level has water surfaces revealing the castles' walls to be red; yet in the film, Ursula's lair is completely submerged and several feet below the ocean's surface and its walls are in tones of purple.
- Flotsam and Jetsam, who are the bosses of Sunken Ship are colored green in the game, however they are typically blue in the film and in promotional artwork. The main reason is the 8-bit's color restrictions.
- In this game, Ariel defeats Ursula in the final round. However, in the film, Ariel ends up surrounded by the whirlpool and dodges Ursula's attempts to kill her, and Eric defeats Ursula by crashing the once sunken ship onto her body.
- Ursula, in her gigantic form during the second battle against her stands atop a platform similar the one in her lair during the first battle against her. In the film, she stands taller than the depth of the ocean.
- In the first scene of the ending, when King Triton transforms Ariel into a human, the beam stays above the surface and Ariel's legs appear. In the film, King Triton dips the trident into the water and then the effects flow through the water until they reach Ariel, yellow magic forms around Ariel, then Ariel goes down below the surface and walks onto the land and with her human legs is now wearing a lavender dress with sparkles.
- In the third and final scene of the ending which shows Ariel and Eric getting married, Ariel does not wear the veil like the film. Also, Ariel's tiara in the game's ending is mint green, as opposed to gold in the film.