Easter eggs
Easter eggs are secrets in video games as a means of unexpected entertainment or a bonus.
The following is a list of easter eggs in Splatoon and Splatoon 2.
Splatoon
Great Zapfish at Piranha Pit
While playing on Piranha Pit, the Great Zapfish appears briefly out of the water on the far, lower west part of the map. If a player waits until there is one minute left, they will likely see the Great Zapfish. An E-liter 3K Scope scope is recommended for this, to get a closer view in zooming.
Basketball
On the Shooting Range that can be accessed by pressing 
on the Equipment screen or whilst in Ammo Knights, there is a basketball hoop. If the player tosses a Splat Bomb, into the hoop, their Inkling will say a celebration phrase, much like they would if they were to splat an opponent or Signal. A green sparkling effect will also occur around the hoop.
Password entry
Each number on the password entry screen for Private Battles plays a specific tone when the cursor is moved to it. The corresponding notes and numbers are listed below:
| Numbers | 5 | 0 | 6 | 1 | 7 | 2 | 3 | 4 | 8 | 9 |
|---|---|---|---|---|---|---|---|---|---|---|
| Note | Lower B♭ | Lower D♭ | Lower E♭ | Lower G♭ | Lower A♭ | Higher B♭ | Higher D♭ | |||
These tones are not arranged in order or in a scale, as one would think, but are a bit more arbitrarily placed. It is possible to play the intro to Calamari Inkantation(NA/EU/OC)[a] / シオカラ節(JP)[b] by moving the cursor between numbers in a specific pattern, which might explain the way the notes are arranged.
The pattern is as follows, each row corresponding to a bar of music:
7 6 7 6 7 6 7 6 5 6 7 6 7 6 7 2 3 8 7 6 7 6 7 6 7 6 5 6 7 2 3 8 3 2 7 2 3 8 9 8 3 2 7 6 7
Sunken Scroll flipbook
Each Sunken Scroll has a doodle of a Character on the bottom right corner. By quickly moving through the pages, one can see a flipbook-like animation showing the character spin around twice and turn into a different one. It starts as a Zapfish, then changes into Judd, and finally, into Sheldon.
Squid Sisters wave
To the left of the Battle Dojo in the elevated walkway to the right of Inkopolis Plaza, there is a studio where the Squid Sisters can be seen chatting. By staying near the window, the sisters will eventually wave at the player. Using the first person view with 
allows one to zoom in on the scene.
Dumpster Zapfish
There is a stuffed Zapfish in the open dumpster behind Cap'n Cuttlefish's manhole in Inkopolis Plaza. Stuffed Zapfishes are used when the real Zapfish for the level have already been collected by Agent 3.
Mysterious Noise in Boss Arenas
After some boss battles, if a player listens long enough, a sound file containing many mysterious and disturbing noises, including steel banging and assorted, distorted screams, will begin playing. Splatoon;s director, Tsubasa Sakaguchi, was not aware of these disturbing noises until an interviewer brought it to his attention.[1]
The mysterious noise won't occur after killing the boss in The Ravenous Octomaw! in Area 4 in Splatoon. These sounds still play in the amiibo Boss battle challenges.
Ability Reroll sound
When you randomize your gear, a sound effect plays. If you slow down this sound to 50% of its original speed, it sounds similar to the Nintendo Gamecube Startup sound:
Splatoon 2
Lobby music changer
Pressing various buttons and moving the joy stick on the Joy-Cons or the Switch Pro Controller activates various sound effects that change the Lobby music in various ways.
Off the Hook wave
To the right of Inkopolis Square, Off the Hook can be found in their studio, where they record the news. By staying near the window, the singers will eventually wave at the player. Using the first person view with allows one to zoom in on the scene. Marina, first notices the player and waves, while Pearl will notice a few seconds later. This mirrors the Squid Sister's Wave in the first game.
Shooting Range
In the new Shooting Range, there is a windowed room that contains 2 unexploded Suction Bombs, a Splat Bomb with no Ink filled, a disassembled E-liter 3K (Which is not in Splatoon 2) and a Splat Roller with the first games design. This could possibly reference the Splat Roller seen in the first games Shooting Range. There are also a pair of Purple Sea Slugs and a hat on the right side of the wall.
Splatting all three moving test dummies at the same time in the left part of the room, their Inkling will say a celebration phrase, much like they would if they were to splat an opponent or Signal. This mirrors the Basketball easter egg in the first game. Using a Splashdown with the right timing is one way to perform this task.[2]
Inkopolis Tower
In the back right part of Inkopolis Square, past the Crust Bucket, one can see Inkopolis Tower from the first game. This appears to be a reference to how Inkopolis Tower could be seen in the background of various Stages and Octo Valley.
Murch playing Squid Jump
Going to Murch in Inkopolis Square, the player can hear sound effects of Squid Jump coming from his phone, the minigame from the first game. However moving the camera shows the phone screen is blank.
Real World references
The Shoal and the Crust Bucket both feature stickers that resemble the real life American Express and Visa symbols. The Shoal also has a sticker resembling Mastercard. Above the Grizzco Industries building are two posters parodying the real life musicals The Phantom of the Opera and Wicked. A poster promoting the new Wet Floor album resembling the real life Tower Records can be seen above the Galleria. Tower Records promoted Splatoon 2 merchandise and sold a real life Wet Floor CD.
Spyke
To the left of the main Lobby, Spyke from the first game can be seen in a café using a laptop. He is unable to interacted with in any way. He is also seen during Splatfest, only change is that he is staring at the Inklings dancing at the square, not using his laptop.
Legendary Cap
In Headspace, the Legendary Cap from the first game can be seen in the background.
Splatoon and Splatoon 2 features references from other Nintendo games, such as a sprite of a Blooper from the Super Mario series and an Octorok from The Legend of Zelda series, which the former being squid-like and the latter being similar to an octopus.
-
From top to bottom: two Octoroks and one Blooper.
-
Another Octorok found in an Octo Valley level.
-
A Blooper in Urchin Underpass.
-
A Gunion and a Blooper in Flounder Heights.
-
Game & Watch's Octopus graffiti in Ancho-V Games.
