A prototype build for PlayStation All-Stars Battle Royale shows an early character select screen with a set of unused characters:

•Chop Chop Master Onion from the PaRappa the Rapper series
•Captain Blasto from Blasto
•Buzz from the Buzz! series
•A Big Kulche from the LocoRoco series
•Dr. Nefarious from the Ratchet & Clank series
•A Eucadian Soldier from Warhawk
•A knight from Fat Princess
•Um Jammer Lammy from the PaRappa the Rapper series

Notably, Dr. Nefarious is featured in the roster without Ratchet or Clank. PaRappa the Rapper is the most represented series in this roster, and has more characters than any one series would get in the final game including DLC. The knight would appear in Fat Princess' moveset, LocoRoco and Buzz! would be represented through stages, and Blasto would be absent completely.

The developers of PlayStation All-Stars Battle Royale expressed that they wanted Mario as a playable character in the game as a nod to the Super Smash Bros. series.

When Hades appears in the Polygon Man boss fight, there is a rare chance that he will perform a dance akin to a cowboy swinging a lasso while spinning in a circle. This dance originated from the 1995 episode "Viva Lost Wages" of the TV series "The Fresh Prince of Bel-Air", where Will and Carlton are forced to enter a talent contest to win money to return home from Las Vegas. During the talent contest, they performed a dance set to The Sugarhill Gang's cover of the Jerry Lordan-penned song "Apache" (also known as "Jump on It"), and the dance in question was originally improvised by actors Will Smith and Alfonso Ribeiro prior to the episode's filming backstage. The cowboy portion of this dance would later be popularized around the time of PlayStation All-Star Battle Royale's release through an appearance in the music video to "Gangnam Style" by Psy. It is not known if there is any way to intentionally trigger this Easter egg.

PaRappa the Rapper co-creator Rodney Greenblatt had a bittersweet response to PlayStation All-Stars Battle Royale, appreciating that PaRappa was in a new title and finding the game fun, but disliking the presence of PaRappa in a battle game with lots of realistic weaponry.

The developers really wanted a character from Square Enix's Final Fantasy series to make an appearance, but Square Enix refused to loan their characters due to SuperBot being a relatively new team and the game they were developing being relatively new as well.

Lara Croft was planned for the game, but Eidos declined on the grounds that they had different plans for the character and her Tomb Raider series at the time, presumably leading into the series' 2013 reboot.

Sony tried to obtain the rights to use characters and assets from Activision IPs in the game, such as Crash Bandicoot and Spyro, but negotiations fell through when Activision offered a hefty price tag for them.

Developer Omar Kendel stated that he was not a big fan of the game's much maligned Super-Move KO system, and said that if he could go back and redo it, he would.

PlayStation All-Stars Battle Royale was originally conceived as "Title Fight", a competitive multiplayer sidescrolling platformer type of game, but after the developers didn't jive too much with that idea it was instead turned into a competitive 4-player fighting game in the style of Super Smash Bros.

At the start of the planning phase of the game's development, Sony first went to their frequent collaborators, Naughty Dog, but they turned the project down due to wanting to commit their whole development time towards The Last of Us. Sony then approached many other of their studios, but all others were busy with other projects. So Sony had no choice but to create an original studio, SuperBot Entertainment, to fill the void.

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".

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.

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.

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.

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.

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.

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."

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.

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.

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.