Easter eggs

Being highly non-linear, the Katamari Series is quite easily given to hiding references to Bandai Namco, other video games, or even the series itself. Often, simple objects in game will be arranged as a reference of some kind and can either be out in the open, or can be hidden and only seen under certain conditions.

Katamari Series[]

Easter Eggs in all of the games of the series include:

The NA, M, and CO save files
- The "NA" meows when rolled up, most likely referencing the Japanese cat sound "nya"
- The "M" moos when rolled up, because "moo" starts with "m"
- The "CO" clucks when rolled up, most likely to reference "cock-a-doodle-do"
Moving objects and characters often represent a katamari being rolled. This occurs in stages for all of the games.

Katamari Damacy[]

The "Jumbomen" may be a reference to the classic Japanese TV hero, Ultraman.
If you hit the Katamari on an item at a certain angle, the katamari will float in midair. It will not fall back on the ground until you hit another item. You can see a video of this on youtube.
In the "Make Gemini" level, one of the twin criminals is named Lupin, which may be a reference to the master thief protagonist of Lupin the Third.

We ♥ Katamari[]

In the Racing level, several cousins can be seen rolling objects in around a house, referencing the race that takes place during the level.
In the same level, a "Happy Flower" can be seen sticking out of a duct stuck in the ground, reminiscent of the Piranha Plants of the Mario Bros. series
An arcade game machine plays the Pac-Man theme when rolled up
On the sumo-wrestling level, there is a copying machine with The Prince on the top, and Slip, a flat version of Prince, coming out of the tray.
On the Make a Planet 3 level, there are several moles surrounded by "funny hammers", similar to the Whack-a-Mole game.
In Make a Planet 5 near one of the starting areas, there is a female ghost that rises up and down out of a well, like the character Okiku in the Japanese folktale Banchō Sarayashiki. (This is also reminiscent of the character Sadako in the Japanese horror movie Ringu.) The same "ghost" also appears in the school as fast as possible level, where it rises up on down out of a toilet in the school restroom.
Another example is the Tsuchinoko, a snake cryptid which can be found in a few levels, notably in the flower stage (popping in and out from a pink flowerbed), the zoo stage (one is hidden in the small bushes where you start and another is in a jar near several cobras) and Make a planet 3 (three are pulling a child who is sitting on a skateboard all around outside the level). In reality, only a few people claim to have seen this snake, and so it is very hard to find in these stages.
There is a creature very similar to a Kappa in the game (actually named as a Kappa in the Japanese version). In fact, the sumo-wrestling level contains two “kappa” in the large pool near the opponent.
In the flower level, a lady titled 'God' when rolled up can be found in the pond with a bear.
Before the 60m mark, in the New York area there’s a skyscraper and a giant gorilla on top of it, this is a reference to the movie “King Kong”, rolling it up reveals the name too.
In the Flowers stage, the player can find seven dwarfs, this is a reference to "Snow White", although the dwarfs in the game don't have any names relating to the actual seven dwarfs, but they're represented by color.
In Chapter 9, The Queen is seen reading a book titled "1 Up", with a mushroom on the other side. This is a reference to the Super Mario Bros. series.

Me & My Katamari[]

The Nazca Lines that you can pick up may be a reference to the earlier Namco game Xevious.
If you loose your mass whilst inside a building or out, you'll be able to pass right through the doors trying to exit or enter. For example if you're in a town portion and you lose your mass and are at a size of under 20cm, you'll pass through the door of the one building you can enter and fall through the stage. If you lose your mass on the inside, you'll be able no roll around out of bounds.

Beautiful Katamari[]

There are Pac-man arcade cabinets that play its theme when you roll it up in the later city levels.
The Coolhouse stage has many Xbox 360 consoles and controllers in the house and around the pool , including a collection of controllers arranged that spells out 360.
Re-entering Egg School as Marcy makes the hiding cousin the The Prince.
If you roll around with a cousin on the katamari, you’ll notice that the cousin’s face will detach from its body, this can be easily observed while rolling only the cousins in Dangerous Colony.
In Roller Roaster, if you leave out the window without advancing to the outside, you’ll end up with an infinite loading screen.
In Roller Roaster, climbing the tower by the river will give you access to out of bounds.

Katamari Forever[]

After the 3km mark in the game, you’ll notice that the coastlines for any continent will not match up, and you’ll see the actual coastlines for the planet are flipped vertically for unknown reasons.
In levels like Make a Star - Danger and Wake up The King!, The Radish Islands, Parsley Islands and Duck Islands that make up the entirety of the island with Machu Picchu and Mt. Rushmore totally vanishes once you reach 300km, this doesn’t happen in Beautiful Katamari.
There are some whales in Make a Star - Danger where they don’t move at all when compared in Dangerous Colony.

Touch My Katamari[]

In Maid Heaven, there is an anime store owner that is supposed to represent Meito Anizawa from the anime "Lucky Star".
Taira no Kagekiyo from "Genpei Tōma Den" is found in the Athlete Abyss.
Toro and Kuro from "Doko Demo Issyo" can be found in Downhill Race and Katamari Fan Festival along with Suzuki, Pierre, Jun, and Ricky from the same series.
Touch My Katamari had a DLC stage based off of the manga Usagi Drop.