In the game's Backer Credits, backer Mighty No. 5040 is listed with the name "Kamiya was right". This is in reference to comments made by Capcom alumn Hideki Kamiya on Twitter about Mighty No. 9 and its producer Keiji Inafune before its release, calling the game a copy of Mega Man and "an insult to their old home", in addition to comments about Inafune not actually creating Mega Man (Inafune's design for Mega Man that would define the series' art style was based on sprite work and a basic concept originally created by Akira Kitamura) and calling him a business man.

In the level "Highway", a billboard of Arin Hanson, popular YouTube animator and co-host of the web series Game Grumps, with the tag line "Face In The Game!!" can be seen passing by. Anyone who had pledged to the game's Kickstarter $2,500 US or more could have a 2D representation of their face somewhere in the game. Arin also appears in the game's credits as 'Mighty No. 12226'.

The game's credits run for almost 4 hours. The credits mostly consist of backers who helped pledge to the game's Kickstarter, a total of 67,226 different people.

Handheld ports of the game for the Nintendo 3DS and PlayStation Vita were planned after a $3.5 million dollar stretch goal for the game's Kickstarter campaign was reached. The ports were passed around to two different developers, Abstraction Games and Engine Software, but their development was marred by issues preventing Unreal Engine 3 from running on the 3DS, a botched attempt at a demake of the game, and delayed communication issues with developer Comcept. Despite work on the ports eventually dying down in 2017, Comcept never formally announced they were cancelled, with their last update claiming they would be released at the end of that year.

The United Kingdom branch of online retailer Amazon would continue accepting pre-orders for the unreleased 3DS port for over eight years despite it being listed as unavailable in other regions, while the PS Vita port was never available to pre-order. This availability period surpasses the game's release on other platforms in 2016, Comcept's acquisition by LEVEL-5 in 2017, and the discontinuation of the consoles the ports were planned for. The listing most likely stayed up for that long because the branch was simply unaware of the port's development ending and nobody bothered to inform them. It wouldn't be until 2025 that Amazon UK finally listed the 3DS port as being out of stock and started issuing order cancellations, with the order drawing attention to this having originally been placed in 2022.