These are all identified vehicles that have appeared in Steven Universe, but hold no significant nor recurring role.
The boat is white and has a small square cabin with wood paneling around the bottom and a lifesaver hung on the side. It has a loud horn which can be heard across the town. The smaller speedboat has two seats and an outboard motor.
Its first appearance is during "Onion Trade", when Yellowtail briefly pulls up to the docks to visit Onion before going back into the ocean again. In "Steven and the Stevens", Greg can't make it to Beach-a-Palooza because Yellowtail accidentally crash his boat into the car wash, damaging it quite badly in the process. Later in "Steven Floats", while Steven was unable to control his new floating powers, Garnet hands him the Boat in hopes to weigh him down but after realizing it wasn't helping, he lets it go. Though in "Drop Beat Dad", Yellowtail uses the speedboat to bring Sour Cream his DJ equipment after Marty ruins his show by trying to advertise Guacola. He also brings the bigger boat in close to shore and uses it to hold a floodlight.
The Inflatable Raft is a raft that first appeared in the episode "Cheeseburger Backpack". Steven packs the raft in his Cheeseburger Backpack for the Crystal Gems' mission to restore the Lunar Sea Spire. When Steven and the Crystal Gems need to cross over a river that forms in front of them, Steven reaches into his backpack and pulls out the raft. Unfortunately, as soon as he tosses it into the water, it is carried down a waterfall by the current. However, after the Lunar Sea Spire is destroyed and sinks to the bottom of the ocean, the raft pops up at the surface near the Gems, and they get on it to head back home. In "The Test", Pearl refers back to the fact that Steven packed the raft in "Cheeseburger Backpack" so that they did not have to swim home, upping his "grade percentage" for the mission to the Lunar Sea Spire.
S.S. Misery / Li'l Lappy
S.S. Misery, also known as the S.S. Li'l Lappy, is a screw steamer steamship, which debuted in "Alone at Sea". It was rented by Greg using the money he got from Marty in "Drop Beat Dad", but after it was destroyed, the transaction was considered a purchase. Steven and Greg renamed the ship "Li'l Lappy" to surprise Lapis Lazuli. The ship was later damaged by Lapis in a successful attempt to get rid of Jasper and sank in the same episode.
Kevin's Himitsu X-12
Kevin's Himitsu X-12 is a customized sports car, which first appeared in "Beach City Drift". It was driven by Kevin and was used in a race against the Dondai Supremo, driven by Stevonnie. The car's visuals and its driver's character are loosely based off of the reference material; Initial D's Keisuke Takahashi and his FD3S. The FD3S in Initial-D is a third generation Mazda RX-7, who's rotary platform is fairly unique, even among other race-cars. It also bears some similarity to a 6th or 7th generation Chevy Corvette, as well as Racer-X's "Shooting Star". It was destroyed in Steven Universe: The Movie.
The Handmade Spaceship is a toy ship made by Greg and Steven for Pearl to fly to outer space. It only appeared in the episode "Space Race". It was destroyed when Steven was test-driving it and after crashing into a rock. This was probably due to a design flaw.
It appears to be made of wood, with a black seat, a crude windshield, and four small wheels. It has a traffic cone nailed on the front as a nose and two wings attached to the sides with tape. All of these materials were retrieved from the Barn.
After Steven saw how Pearl felt about the Galaxy Warp's Warp Pads being inactive (making other planets inaccessible), he asked Greg if they could build a spaceship so that Pearl could go back to outer space. They spent some time building this crude spaceship, though much to Pearl's disappointment when finally seeing it. The spaceship was destroyed when it slammed into a rock supporting a wooden plank on it as a ramp. After its destruction, Pearl chastised its design vocally, while ironically envisioning plans for a working space ship.
The Mach 2 is the second vehicle built by UUU Space Travel after the Handmade Spaceship, this time with the help of Pearl. It is a prototype of the much larger Universe Mach 3 spacecraft and was made to test Pearl's engine concept. It is piloted by Steven until he is ejected after landing.
It consists of what seems to be a hang glider wing attached to a small gray three-wheeled chassis containing a single seat and the engine. Its lack of a wind shield makes it very difficult for Steven to speak while he is piloting it. It gives out a blue jet of flame when flying.
The moped has a sky blue colored base with jet black wheels and a gray front. It has a black seat and grips, and a single tail light and headlamp.
In "Onion Trade", Onion does tricks on it after running over some packets of Hynes Ketchup. When he was finished, he jumped off the bike, while it was still running, causing it to crash and explode off-screen while he watched.
Soapbox Derby Car
The Soapbox Derby Car is a motorized soapbox belonging to Onion and his friends. It is first seen in the episode "Onion Gang".
The car is red with a large wooden crate on the back. Unlike a regular soapbox car, which generally races down hills using gravity to gain speed, this one has an engine and is capable of climbing steep inclines under its own power. It has enough surface space to seat Onion's entire gang plus Steven.
The Police Cruiser is the vehicle that chased Pearl, Amethyst and Steven in the Dondai Supremo during "Last One Out of Beach City" for running a red light and possibly reckless driving. It drove away when Pearl hid her car behind a billboard.
Mystery Girl's Bike
Mystery Girl's Bike is a motorcycle ridden by the Mystery Girl in "Last One Out of Beach City". She rides it on a journey from the Big Donut to Mike Krol's show in Ocean Town, during which she is briefly pursued by Pearl in the Dondai Supremo.
Steven's Scooter is seen in "Steven and the Stevens" when Steven uses it to get to It's a Wash to meet Greg for Beach-a-Palooza. In the various timelines, he sometimes makes it to the car wash, while other times he is intercepted by his future self/selves. It's seen again in "Bismuth", being among the items held inside Lion's dimension. The scooter is a light blue-green color.
Ronaldo's Scooter is a push scooter appearing briefly in "Beach City Drift". It is the vehicle that Ronaldo brought to the racing event, apparently not realizing that the other participants would be racing cars.
- Onion's Moped resembles the Honda Elite, a moped manufactured from 1984 to 1987.