Twinkle Park is based off of a theme park, and every part of it is designed to give off a magical feel, with neon lights and sparkly objects everywhere. This stage is playable as Sonic, Amy, and Big as their fifth, first, and first stages, respectively.
After being shot down in the Tornado, Sonic is looking for Tails, when Amy finds him and follows him to Twinkle Park, where she gets excited when she notices a sign stating that "cute couples can get in free". She instantly enters the park, much to Sonic's dismay, who is forced to chase after her.
Big's reason for coming to Twinkle Park was that he followed Froggy there, and must try to catch him in the pool in the park.
Sonic starts out on a race track with enemies driving bumper cars around. Sonic must defeat an enemy and steal its bumper car, then take to the track. After this area, Sonic jumps in a roller coaster, then proceeds to run through a variety of amusement park obstacles built around a castle.
Amy starts out by the large swimming pool where she must push three buttons in a certain amount of time to proceed. Afterwards, she heads into the castle, which turns out to be a giant house of mirrors. Afterwards, she proceeds through a short section of Sonic's level before finishing and grabbing the balloon.
Big also starts out in the giant swimming pool area, where he is tasked with catching Froggy. The area is very small, and there aren't many fish here, which can make catching large fish for Big's "B" and "A" rank missions somewhat difficult.
Many people associate this stage with Amy due to the fact that it's important in the overlapping parts of her's and Sonic's story as well as it being her first stage and it being the only stage to have a section that Sonic does not enter.
The music that plays in the area with a race track is a remix of Panic Puppet Zone Act 1's music from Sonic 3D Blast (Sega Genesis version). It is also the music played at the intro of Sonic 3D Blast. The music in the Pleasure Castle section of the stage is an an unused theme from Sonic 3D Blast, originally intended for the Knuckles Special Stage in the game.
When riding on a bumper car, the car speeds up and accelerates faster the more Rings that are collected, eventually capping out at ninety nine. Collecting large amounts of Rings is essential if the player wants to travel at high speeds.
After a certain point, on the grass triangle outside Twinkle Park, the Cart Pass becomes available for all characters. This allows characters not otherwise available (a.k.a Tails) to participate in the bumper car section.
Tails, Knuckles, and E-102 Gamma can also get into Twinkle Park through the use of glitches and/or debug mode. They will start in the bumper car's section; however, the game will put them in an area below the starting point, falling into a bottomless pit forever. If Knuckles or Gamma glides/hovers long enough, they will eventually find the track and can proceed into the level (without hacks, Tails cannot do this, as his flying ability does not last long enough). If the player attempts to enter a bumper car, or attempts to use the bowling launcher with any character besides Sonic, the game will crash. On the PC version however the bumper cars can be used with other characters without issue.
In Sonic's story, a major shortcut can be found right after the roller coaster section. By holding left as the player is ejected from the coaster, he/she will not fall down the hole. The player can then run backwards and fall off the edge, landing on a hidden platform. From here, he/she can Spin Dash to the swimming pool, thus skipping a large portion of the stage. This helps immensely with Sonic's A-rank mission.
Outside of Twinkle Park, there is an orange ball with a star in the middle which suspiciously looks like a Dragon Ball from the Dragon Ball franchise.
The Black Hover Cart is the fastest out of all the hover carts.
Every character is accessible to the part outside the castle, though Amy is the only character that can go inside it. If one glitches behind the door on Sonic or Big's variant of the stage they will find nothing.