In December 2023, information spread about Warner Bros. Discovery, which owns Cartoon Network among other major animation brands, potentially merging with Paramount Global, which owns CN's long-standing TV animation rival, Nickelodeon among other animation IPs. Although this deal would not come to fruition at the time, Nickelodeon All-Star Brawl game designer Thaddeus Crews commented that he would take the chance to work on a Cartoon Network vs. Nickelodeon fighting game "in a goddamn heartbeat".

There is an unused model of the Statue of David by Michelangelo in Squidward's prop set. This was likely intended for his air down strong, where he slams down with a block of marble, referencing the SpongeBob episode "Artist Unknown", where SpongeBob makes the same statue by accident. The model has a clam on its groin as censorship, just like in the original episode, but does not have the nose Squidward places on it.

In Garfield's alternate costume texture, there is a portion devoted to Garfello, Garfield's Ninja Turtle alter ego from the Garfield Meets the Teenage Mutant Ninja Turtles short comic published in the 1992 Teenage Mutant Ninja Turtles Magazine.

In the launch version of Nickelodeon All-Star Brawl 2, GIR's voice lines were not artificially pitched up as they were in the Invader Zim series, making it sound as if they had got a very poor replacement actor to those not familiar with how GIR's voice was originally made. GIR's voice actor Rosearik Rikki Simons pointed this out on Twitter, and it would be resolved in a latter update. However, the updated GIR voice lines still don't have the digitizer voice filter he had in the original series.

Originally, Donatello's Super Move was intended to be slightly different. Instead of driving the Turtle Van and shooting lasers at opponents with the other 3 Turtles, he would've perched atop the van alone, remote in hand, and rammed opponents directly.

In Nickelodeon All-Star Brawl 2, Korra has three neutral specials selected based on the context of their use: a water projectile in the air, a non-offense based slippery puddle on ground, and a torrent of damaging water that goes up and down when used with Slime, regardless of location. This move was originally going to function like it contained three extra special moves in the place of one, where you could do another direction input after starting the move to choose a form (not unlike like Gerald's down special move in the final game). When the move was reworked due to its complexity, it was decided to "shuffle around the pieces" into something more easily understood to avoid wasting finished animations and props and having to make new animations close to the deadline.

Rocko's model in Nickelodeon All-Star Brawl depicts him with underwear underneath his Hawaiian shirt, something that is not true of his standard character design in Rocko's Modern Life. This change was reverted in Nickelodeon All-Star Brawl 2 to match his original design.