Koopa Clown Car
The Koopa Clown Car first appeared in the final boss battle of Super Mario World, in which Bowser rides it across the arena. It holds a seemingly infinite supply of Big Steelies and Mechakoopas for Bowser to attack Mario with, and in the last phase of the battle it directly attempts to crush Mario. Princess Peach is also kept prisoner in it and during the battle occasionally aids Mario by throwing Super Mushrooms at him.
The Clown Car made several reappearances in later games as one of Bowser's main means of transportation, often during cutscenes. The Koopalings ride the original Koopa Clown Car all together in New Super Mario Bros. 2. Mario Kart 7 introduced the Koopa Clown kart, which resembles the Koopa Clown Car on wheels. Super Mario Maker included the Koopa Clown Car as a level element, which can be ridden by Bowser, Bowser Jr., the Koopalings (as of Super Mario Maker 2), other enemies (such as Goombas), and even Mario himself.
New Super Mario Bros. Wii introduced Bowser Jr.'s own, smaller Koopa Clown Car, the Junior Clown Car, although it was not officially given this name until the release of Mario & Luigi: Dream Team which he uses to battle Mario; he also uses his father's Koopa Clown Car much later in the game. Beginning in New Super Mario Bros. U, the Junior Clown Car has been augmented with boxing gloves attached to mechanical arms.
The Koopa Clown Car appears as a normal trophy, randomly obtainable after getting at least 250 other trophies.
Bowser's single-seat, personal airship doesn't exactly handle like a dream, but it wasn't designed to be sporty. The Koopa Clown Car was made to carry Bowser's huge weight, not to mention a logic-defying arsenal of massive bowling balls. In Super Mario World, Mario busted the Koopa Clown Car by pelting it with Mecha Koopas.
The Koopa Clown Car's only appearances are in the Bowser Kidnaps Peach/Zelda cutscene in the Subspace Emissary mode, in which Bowser, having stolen a trophified Peach/Zelda, uses it to escape from the heroes. It also appears in the Falco Appears cutscene.
As a fighter ability
Bowser Jr.'s personal Junior Clown Car is featured in Super Smash Bros. 4 and Super Smash Bros. Ultimate, where he rides the vehicle in battle. The Koopalings, which appear as Bowser Jr. alternate costumes, use a different, mass-produced model that made its first appearance in Super Smash Bros. 4.
Bowser Jr. and the Koopalings take 0.88× of the damage an attack would usually deal if the Junior Clown Car is hit. However, if their body is hit, they take 1.15× of the usual damage instead. In Super Smash Bros. 4, the body hurtbox has priority over the Car hurtbox, causing Bowser Jr. to take more damage than usual on average. In Ultimate, this is reversed, with the Car having more priority and Bowser Jr. taking less damage as a result.
The Junior Clown Car features its boxing gloves from New Super Mario Bros. U, used for multiple attacks. Its Clown Kart Dash loosely resembles the Koopa Clown from Mario Kart 7, while it can deploy Mechakoopas as a reference to Super Mario World. Other than these examples, most of the Junior Clown Car's features are original to Smash.
As a background element