Director Ryota Niitsuma has stated that Blade was considered as a playable character for the game, but they decided not to include him as they didn't want too many characters that use swords.

There is code in the game's data that would suggest that Doctor Octopus would have appeared in the game as a playable character.

Dead Rising's Frank West was originally meant to appear in the original Marvel vs. Capcom 3 as a playable character. However, Frank was cut from the game for causing unspecified lag issues. Interestingly enough, it was confirmed that the helicopter pilot Chun-Li was riding into the S.H.I.E.L.D. helicarrier in the second promotion cutscene of the original Marvel Vs. Capcom 3 was Frank West. Frank West's silhoutte can also still be seen in the background of one of the original Marvel Vs. Capcom 3 promotional art pieces. Frank West would later become playable in Ultimate Marvel Vs. Capcom 3.

There is a mistake in Chris Redfield's ending. In the ending, Chris has Albert Wesker on trial with Matthew Murdock (Daredevil) prosecuting. Matthew Murdock was never a prosecutor, as he is a defense attorney.

When Deadpool defeats Magneto he says "I just beat Mag-freakin'-neto! Where your curly mustache at?!" This line comes from a video featuring the gameplay and voice of Marvel Vs. Capcom 2 world champion Michael "Yipes" Mendoza, in which he says the same thing.

Sentinel's character bio specifies his serial number as COTA-94. This is a reference to Children of the Atom; the first Capcom fighting game to feature X-Men characters, released in 1994.

Instead of using Iron Man's original theme from Marvel Super Heroes or writing a new one, they used a dance remix of War Machine's theme from Marvel vs. Capcom: Clash of Super Heroes.

During Ryu's ending, when he is facing off against Iron Fist in a fighting tournament, a board for an upcoming match of Ken versus Mr. X can be seen. It is unknown if this is referring to one of the characters called Mister X from Marvel's universe or Mr. X, the T-103 Tyrant from Resident Evil 2. None of these possible characters, in addition to Ken, are playable in the game.

When Deadpool starts his Level 3 Hyper Combo, he strikes a pose and says "Boop-oop-a-doop". This is a reference to the catchphrase of the classic cartoon character, Betty Boop.

In a Q&A, the developers revealed that Shuma-Gorath was one of the first Marvel characters proposed, but Marvel was reluctant to allow them to use him, but Capcom eventually convinced them that he is popular and a big part of the series history, eventually leading to his inclusion as DLC.

According to Marvel's then-manager of licensed games Chris Baker, one of the voice lines he was able to contribute to the game was Deadpool repeatedly yelling "BANG, BANG, BANG, BANG!" whenever he performs the "Trigger Happy" special move. He confessed to taking the idea from the 2003 Futurama video game, where Philip J. Fry says the same thing when firing a gun.