A new bomb-type sub weapon – the Fizzy Bomb – was added.
A new special weapon – the Booyah Bomb – was added.
A second special weapon - the Ultra Stamp - was teased, but was not yet included in this version and was added in 4.2.0.
Music
Four new battle music tracks were added.[2] The tracks are from two new bands, SashiMori and Diss-Pair.[3]
Skipper Pavilion, the final regular stage to be added to the game, was made available with Version 4.1.0.[4]
Splatfest
Version 4.1.0 added SplatoweenSplatfest data.[5][6] New Inkopolis Square decorations, graffiti, gear, and a start screen sound effect were added for the event. All of this content added to the game was naturally not available to players until the in-game announcement of the event, when decorations started to be added and the gear was made available by means of a Nintendo Switch news article.
Balance changes
Main weapons
Specifications for some of the main weapons have been changed.
Fixed an issue causing a player super jumping to an ally's location in the midst of returning to their starting location after using an Inkjet to super jump into unintended locations when network connectivity was poor.
Fixed an issue when dodge rolling on the inside of a grating, in which the player mistakenly rolled the same distance they would when on the ground although they were moving in midair.
Adjusted the sound effect caused when an opponent enters the area of effect of Toxic Mist, making it easier to distinguish if they are nearby or far away.
Fixed an issue preventing players from tossing a bomb or clam when using the Nautilus 47 if the bomb or clam was thrown at the same time the charge from a stored charge shot expired.
Fixed an issue on the stageStarfish Mainstage, causing player movement to become slowed slightly when moving across a specific slope near the spawn points.
X Power and League Power in Ranked Battle
When playing Ranked or League Battles as a pair, your rank meter, X Power, or League Power will no longer decrease when playing with fewer members on your team due to internet disconnections for an even shorter period than was previously the case.
If internet disconnections prevent a player from finishing enough matches out of the last few dozen matches played, the decrease to their rank meter or X Power for each subsequent unfinished match will be greater than it was previously.
Salmon Run
Players are now able to review stats for their last 50 Salmon Run jobs via the SplatNet 2 portion of the Nintendo Switch Online smart device app.
Fixed an issue causing players to take contact damage if they had been standing in the location an enemy appeared just prior to that enemy's appearance.
Other changes
Voice chat will now be available via the Nintendo Switch Online smart device app when playing with friends in certain modes, even when creating rooms without selecting "Online Lounge."
Players can also choose not to enable voice chat when creating rooms in this way.
This applies to the following modes which previously functioned with the Online Lounge feature: League Battle, Private Battle, Splatfest Battle (Normal) with friends, With Friends (Salmon Run).
Fixed an issue occurring after Splatfest Battles, in which the Splatfest rank meter would go up continuously and repeatedly.
Fixed an issue occurring in Splatfest Battles while under the effect of food items that increase experience or money, in which the player failed to earn gearability chunks even after their Splatfest Tee had reached its highest level.
Fixed an issue in which players wouldn't be recruited after selecting "Recruit more players" when creating a Splatfest Battle (Normal) room after first choosing "Online Lounge."
Fixed an issue when using an amiibo to change equipment in the lobby in which the vibe meter at the top of the screen would mistakenly display information for the weapon used before making the change.
Fixed an issue causing certain sound effects not to play when doing recon on the stageStarfish Mainstage.
Fixed an issue causing platforms on the stage Ancho-V Games to move more during recon than in a battle when hit directly by a shot fired while using the Inkjet special.
Video
On 2 October 2018, a day before the update's release, the Japanese Splatoon Twitter account and Squid Research Lab Tumblr account linked to a YouTube video showcasing some of the new features in the update. The video shows the automatic spectator camera function in Private Battle mode that was added in Version 4.0.0. It is a Splat Zones match on Skipper Pavilion, with Entropical as the background music, and with two of the players using the Kensa Dynamo Roller (showcasing the new Booyah Bomb) and the Kensa Luna Blaster (showcasing the new Fizzy Bomb).[7][8]