Miiverse

Miiverse is a social network accessible on Wii U and Nintendo 3DS. It is integrated into software such as WaraWara Plaza (bustling plaza) to bring people together in order to communicate and comment on certain games and software. The network is built similarly to Twitter, as players can "Yeah" (like) and flag comments and posts, as well as follow or befriend other users. Originally available only on Wii U, Miiverse was later released on the Nintendo 3DS family as part of a major system update in December 2013. A browser version of Miiverse is also available for access on smartphones, PCs, and tablets. Another major renovation was updated in August 2015.

New Super Mario Bros. U
New Super Mario Bros. U is the first main Mario title to incorporate Miiverse. Miiverse in New Super Mario Bros. U is used to create comments on specific courses that either inform, advise, or comment on the course itself. Players are also able to use Miiverse to create snapshots/replays of their accomplishments or results of Challenge Mode or Boost Rush Mode and post it on community forums.

Nintendo Land
Miiverse in Nintendo Land works similarly to Miiverse in New Super Mario Bros. U, with the ability to take snapshots of the results of attractions and post comments on the plaza to inform, advise, or communicate with other players.

Game & Wario
A minigame similar to the Sketch minigame in Game & Wario can be played with other users on Miiverse in a mode called Miiverse Sketch.

Super Mario 3D World
In addition to being able to post to Miiverse while playing Super Mario 3D World, players can also collect Stamps in the game, which can be used to customize posts with images of characters and items that are found in the game. Players can also see others players' Miiverse posts after completing every course and on the world map.

Mario Kart 8
In Mario Kart 8, players can share replay videos of an entire race, or a shorter video created by the software showing the highlights of the race. Players can also view and comment on others' videos. This is done within the software through a feature called Mario Kart TV, not within the Miiverse software itself. Additionally, players can use Stamps to customize their posts, just like in Super Mario 3D World.

Super Smash Bros. for Wii U
A Miiverse stage is set to appear in Super Smash Bros. for Wii U as free downloadable content. Miiverse posts by other users will appear in the background cheering characters on. As of the version 1.0.6 update, players can also share photos replays, custom stages, and Mii Fighters via Miiverse.

Super Mario Maker
In Super Mario Maker, players can post Miiverse comments on levels people have created. Additionally, any level uploaded will also be shown on Miiverse in the in-game posts section in the Super Mario Maker Miiverse community.

Usage in Nintendo 3DS games
Miiverse was released on Nintendo 3DS systems on December 9, 2013 with a limited number of game communities. Initially, there were communities for Mario Party: Island Tour, Mario & Luigi: Dream Team, Mario Kart 7, Super Mario 3D Land, New Super Mario Bros. 2, Mario and Donkey Kong: Minis on the Move, and Luigi's Mansion: Dark Moon, as well as a few other games. Players can access Miiverse by tapping the icon on the Home menu.

Super Smash Bros. for Nintendo 3DS is the first and only Mario 3DS title to have full Miiverse integration at this time. Super Smash Bros. uses this to post photos from in-game.

Mario installments with Miiverse
 

Other installments with Miiverse
NOTE: The game shown below is not directly related to the Mario game series, but does contain references to the series.