There's a lot of sneakily hidden and outright dastardly aspects to Gurumin. There's information about it around the internet, but unfortunately, despite how great it is, this is a niche game and the information is either outdated information that applies only to the PSP version, or is inaccurate/doesn't exist at all.

This short guide should help serve as an amalgamation of all the information. Secrets, glitches, nastily hidden collectables that no sane man should be expected to immediately know, the usual.

This is very much a work in progress.

This section will remain vestigial and useless until I go through and nab shots of all the sneaky collectable and monster spawning locations.

As some general tips:

• Look behind yourself after exiting every door, archway, and anything else that obscures your view of the area behind you.
  
• Destroy all destructible environmental objects. Some latter levels hide monsters up trees or in rocks.

It's tedious, but this will guarantee that you will get almost every collectable/monster.

Until a detailed guide is added, just use this:


Note that this is not my video guide, but it does contain the locations to all 11 Platinum Medal locations.

Most Picture unlocks are fairly simple, but here's a simple reference anyway, in the order that they're listed in the Desk Menu.

"Lots of Roofs"

• Give the Joke Glasses to Chucky
  
• Speak to him a few times
  
• Quiz the NPCs in the area
  
• Speak to Chucky again

"Evening Stroll"
Hyperbolic will taunt you about a hidden Platinum medal in the village at some vaguely defined point in the story. Find it and return it to him.
It's hidden in the Fireplace in Hyperbolic's house.

"Gas Mask Manga"
One of the Mystery Bags will have Pamela pull out a diamond. From there, simply talk to all the NPCs in the town before leaving the area, to automatically initiate a trade. It's a giant trade quest.

Warning: Several of the items in the quest can be accidentally consumed from the menu. If this happens, either reload a previous save, or else tough luck bro; better luck next playthrough.

"Everyone's Story"
This one is not fun.

You have to change into a different costume while Puchi, the dog, is in the house. The NPC's walk patterns are entirely random, so you may just have to wait around and follow the dog before he randomly decides to walk into the house.

From there, it's simply a matter of quizzing all the NPCs before Cylinder gives you the Picture.

"Nap Time"

• Give the Afro, randomly gained from Mystery Bags, to Poco
  
• Hit him with either a Guard Dash Special or plain Spinning Special, while using the Flame Parts.

"Devices and Gear"

• Give the Pharaoh hat, randomly gained from Mystery Bags, to Rocky
  
• Hit him with a Charged Drill Attack

"A Young Hero"

• On your second playthrough, buy out all of Disk's shop supplies (this includes any items added by speaking to him with different costumes, so be careful about that)
  
• Leave the area and speak to him again.
  
• To put up an ad, face a wall (or statue) when a prompt appears and press the action button. There are three ads.

"A Boring Class"
Towards the end of your first playthrough, Fan will pester you about paying for the damage that the Shapeshifter wrought. To pay off your debt, wear the Maid costume gained by donating 99, 999 Pockles to the vending machine in Shadow Grotto to initiate a minigame.

The text inputs are, of course, case sensitive.

"Yearning for Home"

• Give the Sombrero, randomly gained from Mystery Bags, to Pierre.
  
• Find his bird in Monster Village.

Some short tips for all the Minigames.

Doc's Lab
This one should be a breeze, provided that you only initially hit the 20 lazer mark on the first expected run. Each successive set of 10 that you hit over that raises the bar to get a gold medal.

Getting 80 lazers might be easy, but getting 150 is not so fun. Make sure to end the initial guinea pig run as soon as you get 20 lazers, and it'll be dandy.

Mole Dojo
While releasing a pent-up drill attack, hold the attack button while drilling to immediately start charging up another drill attack, without having to throw out the initial attack. This should cut down your time between charges enough to easy breeze through this minigame.

Pecky's Mansion
Abuse jump attacks. Your special attacks are disabled for all minigames, so you can easy spin in midair to hit moles from across the map.

You can hit them for extra while they're still burrowing, and with a little maneuvering you can jump attack them into the border of the whack-a-mole arena and get them for extra.

Hoccer
Solely play defender. You have no chance against Motoro, he will out-maneuver you every time. Your only chance is to jump attack the ball if it gets near your end of the court, and hope to hell and back that Motoro doesn't decide to play the role of Attacker.

Motoro will destroy you many times. Try to take it on the nose.

Some odds and ends that don't belong in any other section, but are otherwise important to know.

"S-Ranking" a difficulty mode.

• In order to get the "fully completed" achievement, you DO need to fully complete every level. However in order to "S-Rank" a difficulty mode, you need to leave a single level NOT S-Ranked/Mastered. I recommend leaving Blackbean till last.
  
• Obviously, don't save over your data if you intend to get both achievements.
  
• Minigames DO NOT count towards the S-Rank count. They are not levels. They serve only to get you gold medals. You can safely skip Hoccer and still get the full S-Rank achievement.

Differences between PSP version and PC version

• Every "Give 30 gold medals to Hyperbolic" costume is not present in the game. So really, no need to punish yourself with Hoccer. The Hair Buns aren't that great.
  
• The Pockle limit is 99, 999, not 65,500. This only really comes into effect with the Maid Costume.

Effects of carrying over Save Data

• You will need to repurchase all Hats, including gold-medal ones.
  
• Gold-Medal hats you have purchased in the last playthrough drop to a 1 coin purchase for the next. However, the last Hat will ALWAYS jump to 28 Gold Medals after you have gotten the other two. This means you can put yourself into an unwinnable state by not getting the Monkey Cap, which you need for Pecky's segment.
  
• The Master Drill, Pictures and all Costumes directly carry over.
  
• After the prologue, Cylinder directly offers you all special skills without having to progressively beat bosses. You will have to repurchase them, though.
  
• All Pockles, Pictures and Junk carries over through the save states. Medals do not.

Mystery Bags
The order in which you are given hats is completely random, however you will receive every single hat by the end of the game, as long as you find every Mystery Bag in the game. This order changes every playthrough.