Below is a listing of various easter eggs within the game.

Compass-chan Surprise

Kancolle Easter egg?
Kancolle Easter egg?
Compass-chan surprise.png
NO DATA-Kuma.png
When you get a ship drop, extend the flash object and click on the upper left third of the black area (the cursor will change to a hand) to get the COMPASS-CHAN CLASSICAL DANCE PARTY.

It seems to have been removed on December 2014. Instead it was replaced with an image of a black colored ship girl with NO DATA printed on the anthropomorphise version. Since sometime around then till now, the NO DATA variant has now been removed for just a simple background, the voice line, voices and the caption but no actual image of the ship girl herself.

Some more information about it can be found here (albeit in Japanese only): http://kancolle.doorblog.jp/archives/35481633.html
As well some Google search results (albeit again in Japanese): http://goo.gl/L8BYDG Extended version of the "compass-chan classical dance party" music is found here: https://youtu.be/5TOzc4MfM9I

Non-functional repair cancellation dialog

Undefined ship bug.png
The "cancel repair" dialog is a function that is likely removed from the game. After placing ships in the repair dock, stretch the game window horizontally until there's a significant amount of wide black space on the left and right sides. Clicking on the space on the left will display the dialog, which does not actually cancel anything if "yes" is selected. Note that selecting "yes" also causes various bugs to occur.

Re-clicking the black space again (by cancelling the window for the first time and clicking on the black space again) will sometimes show not an "undefined" ship but also a random ship that is currently in your possession (it can even show a ship that is currently going on an expedition).

SHIRATSUYUINGLITCH.png

Jumping Construction Girl 

Kancolle Easter Egg At Construction Place
Kancolle Easter Egg At Construction Place

This common easter egg only happens when you begin constructing a Ship girl, and clicking on that particular construction girl with a ponytail carrying boxes.

Unimplemented features

By taking apart the flash game client, one can discover features that are unimplemented, or have been cancelled.

  1. 補給艦 (Supply ship)
  2. 超弩級戦艦 (Super dreadnought)
    • Similar to BB.
    • Historically, almost all battleships (except Gangut) in the game are super dreadnought.
  3. VT信管/近接信管 (VT fuse/Proximity fuse)
    • Usable by all ships except submarines.
    • Appeared on June 12, 2013 update notice together with other AA equipments when it mention equipment AA power increase, with a note that it is unimplemented.

  • Available from extraction for many ship implemented in the game's first 1.5 years but can never be heard in-game.

  • Under kancolle server's directory, a folder with encoded file name as kcrzgndzraoddu contain sound files of unknown kanmusu, which can probably be seen as something dummy. More information maybe found here. (Seems to be removed now.)

At a place like t-this...

Removed/Cancelled Equipment
  • SB2U
    • Was supposed to be introduced in the Fall 2016 Event.
    • Likely cancelled last minute for being anti-historical.
SB2U 199 Card.png
Unused Item
  • 女神
    • Shop item ID=12
    • Asset is still on kancolle servers(2020)
Shop Card 12.jpg
Unimplemented items
  • Development material box (開発資材箱) (small/medium/large)
  • Treasure chest (宝箱) (small/medium/large)
  • Return directive/order (帰還命令書, 帰還司令書)
  • Challenge (挑戦状)
  • Trap detector (罠探知機, 罠探知機・改)
  • Danger detector (危険探知機, 危険探知機・改)
  • Excavator (掘削機, 掘削機・改, 深海掘削機)
  • Clover (よつばのクローバー, 黄金のクローバー) (4 leaf/golden)
  • Compass (高価な羅針盤, 伝説の羅針盤) (expensive/legendary)
  • Blue searchlight (青い探照灯)
  • Mast (銅のマスト, 銀のマスト, 黄金のマスト) (copper/silver/golden)
Unimplemented items.png
Equipment category selection screen at development screen
Unimplemented features.png
In-game message sprites
離脱成功 (Withdrawal success) is what is currently shown with 100% chance (but in smaller print) after day battle, on the top left hand corner of the screen that asks you whether to continue into night battle or not.
離脱失敗 (Withdrawal fail) message might indicate some form of forced night battle was once being considered.
敵艦隊に逃げられた (Enemy vessel fled) message indicates that some kind of mechanism disallowing players from entering the night battle phase might have been brainstormed before.
敵直援戦闘機が妨害 (Obstruction by enemy interceptor aircraft) is a message found together with other statuses for abyssal fleets in the detection stage.[1]
Message sprites.png
Messaging system
Mail feature.png
Sortie node events
When reaching a node, certain events can occur:
  1. Whirlpool: 司令官!うずしおが発生しました!
  2. Huge wave: きゃーっ!! 高波が発生しました!
  3. Bad weather:
    1. 悪天候でこれ以上は進めません。 帰還しましょう! (We can't advance because of the bad weather, let's go home!)
    2. 前方に悪天候が発生していますね。 迂回して進むことにしましょう! (We see bad weather before us. Let's take a detour!)
  4. Octopus: おや…大きなタコさんが何かを持ってきましたよ! (Oh, a big octopus is carrying something!)
In Kancolle RPG, a TRPG edition of the game, bad weather is preserved and can be avoided with a radar.
Octopus.png
Unused fairies
Fairies.png

References

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