There is evidence suggesting that Pikachu in this game is actually Pichu from Super Smash Bros. Melee, albeit evolved:

•Pikachu in Brawl uses Pichu's wall jump ability from Melee.
•Pikachu's Final Smash in Brawl is Volt Tackle, which, in the Pokemon games, can only be inherited by an egg-born Pichu.
•Pikachu's blue costume in Brawl uses the goggles worn by Pichu's blue costume in Melee.

According to an IGN interview, Super Smash Bros. Brawl's motion controls were hard to work into the game, possibly due to their impreciseness. Instead, the game was focused on the Wii's internet capabilities.

Super Smash Bros. Brawl was originally planned as a launch title for the Wii, meant to showcase the difference between the Gamecube and the Wii (mainly via online capabilities), just as Super Smash Bros. Melee showcased FMV and graphical capabilities that the N64 was incapable of.

Yoshi's saddle is missing in the Super Dragon trophy.

Wobbuffet's trophy states that it originated from Pokemon Red and Blue, which is false, as it originated from Gold and Silver.

By looking through the game's disc you can find different victory fanfares signed for each character, there's even fanfares for both Mewtwo and Roy. But in the final game, Meta Knight is the only character with a unique fanfare.

The US version of the Baby Mario trophy claimed that "he lacks overalls", even though the trophy itself depicts him with his trademark red/blue overalls.

Despite not appearing in the Subspace Emissary, Crazy Hand's trophy is placed in The Supspace Emissary category.

The Sothe trophy states that he is a swordsman - this is untrue, as Sothe wields knives and daggers.

Moltres' trophy says that its first game was Pokemon Gold and Silver, when it really originated in Red and Blue.

On the Kyle Hyde trophy, it states that he is a former detective. This is not true; Kyle is a former cop who worked for the NYPD.

The Bonkers trophy says that Kirby could get the Smash ability by inhaling him. This is not correct, as he only gives the Hammer ability.

Lucas' home village is stated to be call "Tazumili" in the US version, but in Mother 3 the village is actually named Tazmily. This was corrected in the PAL version of Brawl.

During the opening cutscene, hidden characters are not shown until they are unlocked, with the exception of Ness, Marth, Sonic and Snake.

The Pokemon Trainer has an unused jumping animation. Some fans have speculated he may have been playable on his own, but it seems more likely that this jumping was planned to help him traverse large areas like The Subspace Emissary.

In the Subspace Emissary mode, There is a cutscene where Ridley grabs Samus and drags her along the wall. He only lets go when Pikachu Zaps him with a Thunder bolt. This cut scene seems to have influenced a similar scene in Metriod: Other M.

In the unlockable All-Star mode, the order in which opponents are fought is based upon the order in which their game series were released chronologically, beginning with Mr. Game & Watch and ending with Captain Olimar.

Peach's Final smash is a piece of Super Mario Bros 3 music sped up. The music is from World 5: The Sky, Coin Heaven bonus levels and in the Warp Zone.

Characters were originally going to visually show battle damage. You can see some of the injured player textures in the games code.

While the Project M Backroom was preparing the release for Project M Demo 2.5, a mod of Brawl that makes it play like Melee, they discovered that there was a bug in the game where button inputs can take anywhere between zero to two frames before being recognized by the game. This means that anytime you press any button in Super Smash Bros. Brawl, the attack might start up later. It is unknown why this happens.

The characters Dr. Mario, Roy, Mewtwo were supposed to make a return, and Dixie Kong, Plusle and Minun, Toon Zelda (Tetra), and Toon Sheik were supposed to appear as newcomers.

Files for these characters (sadly incomplete) can be found in the game's ISO.

Masahiro Sakurai left a picture of his cat in the ice area in the Pokemon Stadium 2 stage.

The texture of the Metroid assist trophy contains a sprite of Earthbound's Mr. Saturn. It can't be seen in-game, as it isn't mapped to the model.

The Announcer (who also voices crazy hand and master hand) is Pat Cashman, who was the announcer for "Bill Nye, The Science Guy". He even acted in some scenes in the show.