If you look inside of the entrance to the Battle Dojo while standing outside, a few Wii U controllers can be seen hanging on the wall. The controllers are a Wii U gamepad, three white Wii U pro controllers, and a black Wii U pro controller.

From June 1st until September 8th, 2015, Canadian Yogurty's and Yogen Fruz stores offered Splatoon-themed flavors and toppings to promote the game. The two flavors available were Squidsicle - a dairy-free mango popsicle sorbet - and Inkberry, a probiotic low-fat strawberry frozen yogurt. Mango or strawberry popping bubbles were also available as toppings.

On June 15th, several select Yogurty's locations also offered customers the chance to play Splatoon while at the store.

When you highlight one of the numbers on the password screen, a music note will play. If you follow a specific order, it is actually possible to play the final boss theme, also known as the "Squid Sisters Song". The required number combination is:

767676765676767238767 676765672343212349432761

In 2015, Nintendo released a free DLC update to Splatoon, adding a costume from the Japanese manga and anime series, "Shinryaku! Ika Musume", or "Squid Girl", giving the player the titular character's outfit.

On the map "Museum D'Alfonsino" during it's Splatfest variant, two inkling statues can be heard making child-like giggling from opposite sides of the map. Strangely, the same sound clips can be heard upon defeating Koloktos in The Legend of Zelda: Skyward Sword.

Since no more Splatfests are being held for the game, this secret is inaccessible without hacking.