Peach's Castle returned as downloadable content in both versions Super Smash Bros. 4 on July 31st, 2015, alongside Hyrule Castle. Like other returning stages from the first Smash game, some of the textures are slightly higher in quality, but the general overall primitive look of the original is retained.
Peach's Castle has two main platforms, one on top of another. It is possible to fall through the top platform. The bottom platform partially makes a block going left to right, that makes sound in Smash 4 if listened to carefully. On the top two corners there are two floating, inward-angled platforms that move slowly up and down and prevent people from being smashed away too easily. These platforms are very easy to DI off of as well. It has a floating Bumper on the middle above the second platform of the stage. This bumper moves slightly left and right (it remains stationary on 1P Mode though). It is difficult for most characters to recover on this stage since the two floating platforms limit recovery to the top platform and there are no ledges that can be grabbed, with the moving black platform on the bottom of the stage greatly aiding recovery, but it isn't always on the side the player is on). In Smash 4 however, fighters can now grab onto the bottom platforms.
The Ω Form removes all features but the main platform, which has been extended.
In competitive play
In Smash 64, for a long period according to the old American ruleset, Peach's Castle was usually considered a counterpick stage in singles. This is because of the inability to grab the edges, meaning that some characters can be gimped or edgeguarded much easier than usual, and because of the Bumper hazard and angled platforms on the side of the stage that can prevent KO moves that would have otherwise KO'd. However, the Bumper can be used for various unique combos, and can also be used by characters such as Pikachu to escape pressure. The stage is often counterpicked by Jigglypuff and Kirby players, and the lack of edges that can be grabbed serves as a disadvantage to characters such as Link and Captain Falcon. However, most recently the stage was banned. In doubles tournaments, the stage is usually banned, due to the listed reasons above along with the fact that the stage is too small.
This stage's elements come from Super Mario 64. The stage takes place in the sky above Peach's Castle; in the background, it can be seen that Peach's Castle is very far below the actual stage. The sign seen on the lower level is also from the game, and the bridges likely are inspired by the broken bridges seen in the Cool, Cool Mountain course. The triangular-pyramidal platforms seen on the upper sides of the stage resemble the ones seen in stages with dangerous ground, like Lethal Lava Land, which moves around in accordance to Mario's placing. Unlike said platforms, these ones do not move at all, let alone are not activated by weight. The structure and platform of the stage, also resembles Whomp's Fortress course.