The gargoyle in the background of the DLC stage, "Graveyard", will comment on characters that are participating in the battle.

Additionally, when talking about Nathan Drake, he will reference Tomb Raider by telling Drake that "these tombs have already been plenty raided".
Contributed by chibirobo
Jak and Daxter's idle animation when not moving for a while will have them high five and then dance, as seen at the end of Jak and Daxter: The Precursor Legacy.
Contributed by chibirobo
Sweet Bot, Sweet Tooth's Level 3, has a machine gun on its right arm. This is based on its concept for Twisted Metal (2012), where it originally had a machine gun, however, it was removed possibly to balance out the game.
Contributed by JelloBoyInc
In Jak & Daxter's ending, Daxter states, "I have a certain girl wearing a certain pair of pants i'm dying to see." This indicates that the game takes place after Daxter received his pants in Jak 3.
Even though Jak's unlockable costume is his racing outfit from the sequel, Jak X: Combat Racing, Daxter still doesn't wear his pants in this game.
Contributed by chibirobo
Nathan Drake is the only character in the game to have intros and outros referencing other characters he is facing. For example, Nathan has an intro of him shown with a page from the Thievius Raccoonus, and he has an outro in which he tells Sully that he "punched a chicken", referring to Fat Princess's Level 2 Super.
Contributed by chibirobo
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Sackboy is much larger in this game; about as tall as PaRappa and Toro. In his own series, he and the other sack people are about 8cm tall.
Contributed by JelloBoyInc
According to Omar Kendall (lead game designer of PSASBR), at one point during development, Cole MacGrath and Evil Cole MacGrath were going to be one character, who would start out neutral, and turn good or evil based on the player's actions. After this idea was dropped, they decided to just use the Hero version of the character.

However, "the IP holders felt really strongly that the way that the Cole character manifests, he really is two different guys, and they felt the character would be best served as two different and they really pushed for it."
Contributed by firemagma122
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Dart from Legend of Dragoon and Abe from Oddworld were both originally planned to be released as DLC characters, but were ultimately cancelled. Concept art was made for Dart, and Abe was announced as cancelled DLC for April and May. Alongside the new characters, there were plans for a Gravity Rush/Journey stage, but it was also cancelled.
Contributed by frankfrost2
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Sackboy's Pop-It is different from the one in the LittleBigPlanet series. This was done to integrate it into a fighting game as all of the icons represent moves done by Sackboy in the game.
Contributed by SRJ
PaRappa's Level 3 super is slightly different depending on the amount of opponents in the match. If there is 1 opponent, the U Rappin' Meter will raise to the "Good" level. If there are 2 or 3 opponents, the meter will raise to the "Cool" level.
Contributed by SRJ
Toro's three different "stances" are based around Street Fighter, Mortal Kombat, and Tekken. One of the moves he can use in his Torobi stance is inspired by Liu Kang's bicycle kick. In his Oni stance, he can throw a projectile similar to the mochi Hadoken.
Contributed by SRJ
PaRappa's intro and ending were made by the same company who did the PaRappa the Rapper anime.
Contributed by gamemaster1991
Nariko, Sir Daniel and Jak are the only characters who's original voice actor did not reprise their roles in this game (though Jak and Nariko have their original voice actors in the Italian version).
Contributed by SRJ
Cole MacGrath, Emmett Graves, and Kratos are the only characters that have an alternate costume based on a different character. Cole's being Kessler, Kratos being Deimos, and Emmett Graves being Logan Graves.
Contributed by SRJ
The game 'PlayStation All-Stars Battle Royale' bears a very similar resemblance to the Super Smash Bros. series in gameplay, but the name also shares a similar resemblance in that the Japanese name for Super Smash Bros. is called 'Nintendo All-Star! Great Melee Smash Brothers.'
Contributed by TrevMaster3000
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The moon in the background of the San Francisco level is the same moon that appears in the logo for Insomniac Games. Insomniac Games created both Resistance and Ratchet & Clank, the two franchises the stage was based on.
Contributed by ataw1993
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The boss "Polygon Man" was actually the Playstation's original mascot from 1995. He was meant to demonstrate the power of the Playstation, but was dropped shortly after the Playstation was announced.
Contributed by DidYouKnowGaming