Focused around video game characters, Wreck-It Ralph features numerous video game characters from multiple publishing companies alongside the film's cast of original characters, much like the 1988 film Who Framed Roger Rabbit.
Ducks from Duck Hunt (as obstacles in Fix-it Felix Jr.)
An NES controller as the vault to Sugar Rush's CPU room.
Mario (mentioned by Felix in the 30th Anniversary party)
(Note: Mario was intended to have a physical appearance in the film alongside his brother, Luigi. However, the producers could not find a place to work them into the story that felt right for their significance.)
Blanka from Street Fighter II (appeared briefly during the closing credits)
Dr. Wily from the Mega Man series was initially set to make an appearance in the Bad-Anon villains support group, but was eventually cut from the final version of the film. The actual reason for his removal has not been revealed yet, but some have theorized that it was because many real life gamers feel that Capcom has treated Mega Man rather poorly, at least in comparison to Street Fighter.
Beard Papa the Japanese cream-puff store brand mascot (as the Sugar Rush candy-kart factory security guard, voiced by John DiMaggio).
Skrillex as the DJ at the Fix-it Felix Jr. 30th anniversary party.
A caricature of Director Rich Moore (seen behind Ralph in Tapper's).
In the scene in which Sargent Calhoun and Fix-It Felix are in Sugar Rush, they land themselves in a river of NesquikSand, made entirely of over-concentrated Nestlé Nesquik.
In the same scene, they must pull themselves out using vines made of Laffy Taffy, which gets attracted to anything they find amusing.
Several Oreo cookies act as guards at King Candy's castle. Their "Oreo" chant is in turn a reference to the guards of the castle of the Wicked Witch of the West in The Wizard of Oz.
In one of the scenes that takes place in Litwak's Arcade and Family Fun Center near the beginning of the film, a soda with a cup that reads Subway is shown on-screen on an arcade game. (That means this movie partnered up for the first time.)
One of the arcade games in Litwak's Arcade is Undead Apocalypse, made by Crosman and Airsoft.
The Sorceress bears a resemblance to the Dark Queen from Battletoads with the coloration of Lillith from Darkstalkers.
The Konami Code is used as the password to unlock the game vault.
Games featured/homaged during end credits
Stage 1 from Q*bert (appearing on the "Screenplay by" credit.)
Chemical Plant Zone from Sonic the Hedgehog 2, with the Flame Mobile boss from Sonic the Hedgehog 3 (Appearing on the Co-Producer credit.)
An 8-bit version of House of the Dead
A "Hero's Duty" cutscene referencing Metal Gear Solid
An 8-bit version of Hero's Duty referencing both Metroid and Super Mario Bros.
Mentions and Allusions
GLaDOS from Portal (used as a nickname by Vanellope to Ralph referring to "stepping out of his comfort zone"; pronounce "Gladys", which is the official pronunciation rather than "GLAD-os" which is the fan pronunciation)
Aerith from Final Fantasy VII (referenced and written in graffiti as Aerith Lives on a subway wall in Game Central Station)
Sheng Long from the Street Fighter series (his name appears as a graffiti at the portal leading to Sugar Rush)
Leeroy Jenkins (shown as graffiti on the Terminal Wall as "Leeroy" and later "Jenkins")