ROGO

Keep shooting your mail at the shop employee. Eventually, she will multiply. Keep shooting, she will keep multiplying. The achievement will trigger a little early (at least it did for me) but after enough duplicates are made, the shopkeeper will move to the exit and say "I DID NOT EXPECT THAT TO HAPPEN"

First and foremost, shooting ANY boss with mail does nothing. All bosses are on a timer, and you need to wait it out.

The plane boss is relatively straight-forward to beat, and considering it's a timer boss there's one set way to beat him and you're doing it. This guide serves to provide tips for those who can't seem to not get KO'd by him.

First of all, play Fu-Chan - i have a guide here on how to unlock her, too. If you have the Frog, then he's a solid pick too but won't help much if you're having trouble surviving. Fu-Chan's starting item, Case, can be used 7 times on this boss map. The cases always contain money, as well as a chance of either a heal (!!!) or a full charge - making it a basically infinite-use item, if it weren't for the limit in place.

Second of all, if you don't know already, mail can destroy yellow bubbles. The orange ones that are shot out can not be destroyed, and must be avoided. Personally, i recommend the Small mail item (frog starts with it and it's available in the shop) but bouncy mail works too.

Third of all, everything that hurts you flashes in this game, and the plane does not flash. Touching the plane (or the soda boss later on) does not hurt you. Of course, it's where his bullets spawn, so you'll get hurt if he's firing, but it's worth noting since there are often times where he does not.

The above 3 tips can apply to most parts of the game. The last tip is exclusive to the plane boss, and that's to stay away from the rightmost third of the screen. Homing planes spawn on that side and home on you from that side. Staying on that side is a death sentence. If you want to stay on the right side, stay close to the center

Once you've done the boss once, it shouldn't be too much of a struggle. Just, good luck if you're playing morning post 😛

I am unable to get any images since once you unlock the frog, he disappears from the map.

(no, it's not the frog npc that's required to unlock fu-chan. this guy looks different.)

The unlock conditions for the frog are simple. You need to beat the soda boss 3 times. I'm unsure if you need to talk to the NPC that spawns afterwards every time, but i did, so stay safe. After your third time, you should be teleported to a largely green area. The frog will be somewhere on the first green level. He blends in pretty well but isn't hard to find if you just look for him. Walk over him and press F and the achievement will pop.

He's also my character of choice, as he starts with the best mail and a tie for the best item!

A simple trick for this boss is to stay in the top right corner the whole time, shooting diagonally (downwards and to the left) as to get any yellow bullets that come your way. Ideally, you will want Small mail, as that has the occasional triple shot, but it's by no means a requirement.

If you don't want to cheese it however, all i can say is that it will take a few tries. I have no specific advice, but it may be within your interest to read my PLANE BOSS guide. The train boss DOES flash though, so he WILL hurt you if you touch him.

Beating the boss will unlock the mechanic, and thus, will stack the achievements.

After you've beaten the train boss, a fish will spawn in the bottom right corner in the same room. All you need to do is walk up to it. The best transition in the game will play, you'll be in the water level, and this achievement should pop.
If you keep going down the route, you will be greeted with the skull boss, and the game will end there instead of the train boss.

This achievement is in the water level. If you don't know how to get there, follow my guide for FISH ARE COOL.

On the second water level, shoot every fish you see. One of them, at random, will expand when shot. It should be obvious when you've hit it.
Once you've shot it enough, it will transform into a bus of sorts. Walk over it, and hit F.

Keep in mind you can do these first 2 steps in the first water level too, but the requirement for the achievement will NOT appear afterwards. You need to be on the SECOND level, since that level is where the protagonist from happy snake's other game, LIBRARY, appears. He looks like this:

Walk over him and hit F. The achievement will pop, and you will unlock an alternate skin for the Morning Post character.

Tip: Fu-Chan is a damn good character. She can carry you through achievements through her broken item. (up until you get the frog, i find him better)

Find the frog in the first area, the pink and green room. He spawns past those parts but seems to largely prefer the first area. Make absolute sure the city bubble is above him - fu-chan is not anywhere else. He and it will look like so:

Go right next to him, press F. He'll fly off-screen (and play the best sound effect in the game.) Continue the level as you normally would, sending mail to the rest. If you have the yellow rolly boy in your level, do not use him. Go to the van. You will be taken to the city level.

Traverse the level until you find the school. It will look like the attached image below. Go over it and press F and fu-chan will unlock and the achievement will trigger.

...watch out for the ufo though

Beat the game with the mechanic. I'm not sure if taking the full route (skull boss) affects this, but going the normal route (just ending the game by riding the van) is far faster.

When you're in the winning area (it's a nice shade of blue with flowers everywhere,) on the first level, a female mechanic character will appear. She looks like this (she's to the right side):

Press F over her and the achievement will pop. The female mechanic skin will not unlock, as that is far more complicated. As far as i know, only the developer knows how to get it, and the requirements involve doing things outside the game (i got it through a bug that was patched right after i got it.) The skin is not a requirement for any achievement, though, so don't worry about it.

To put things simply: you need beat the full game as any character. This entails that you get to and beat the skull boss (duh,) which you access through the secret water level - see my guide for the achievement FISH ARE COOL.

To make your journey easier, i absolutely recommend playing as either Fu-Chan or Frog. Fu-Chan's item, the Case is busted. In any chest, you either get a full charge (which means using your item requires no charge) or... a heal, allowing for some prolonged life. And Frog starts with the small mail, which is the best type of mail in the game, alongside Refrigerate, which freezes then - after a second - destroys all bullets in view. If you choose fu-chan, buy the small mail in the shop if it appears. You start with enough money to buy it.

Second of all, after you've beaten the green/pink, clouds, and soda levels enough time, a 'yellow rolly boy' (as the dev calls him) will appear, allowing you to skip that area. It will take you to whatever's closer, the shop or the next boss. It only appears in the 3 areas i've mentioned - in the green area and the water/skull area, he will never appear. it is a massive time saver, and allows you to get to the skull boss way faster.

After you've beaten the train boss, go to the fish in the bottom right corner. Traverse your way through the water area (pick up the LIBRARY achievement if you haven't yet) and the skull area, and at the end of that the skull boss will appear. He's hard and i don't have much advice for him, just try your hardest to not move left or right unless you absolutely have to. If you survive his onslaught, these achievements will pop and Ghost will be at your disposal.

This achievement is, without a doubt, the hardest in the game. It's not incredibly hard, or even really that hard, but it's rough sailing for sure.

To get this, you need to beat the full game (skull boss) as Ghost. If you don't know how to beat the full game yet, then you haven't unlocked Ghost and should refer to my guide for FISH ARE COOL.

There's not much new to say if you've already beaten the full game, but Ghost is a complicated character so i will provide some advice as to how to play her.

Ghost has the most interesting passive. Playing her adds houses to the map that gives you lil ghosty friends that follow you if you press F over them. If you press space, the ghosts will go towards the nearest bullet and sacrifice themselves. This passive doesn't have much use, personally, but if you want to save them for the skull boss, go right ahead.

Ghost's item, Fanmail, is exploitable. The aim is to use the item with as many entities (not just enemies!) on the screen that can fit, and they'll all give you lovely letters and a good amount of money. However, you can perform this multiple times on the same entity, leading to a loooot of money. Save this money for buying small mail (or bouncy, if small never comes up,) stat boost items, or the Refrigerate item. DO NOT BUY THE CASE ITEM. Ghost, more often than not, gets more lil ghosts from cases than anything else, full charge or otherwise.

Provided you have small mail and refrigerate, you can play the game like you normally would and hope the skull boss doesn't completely annihilate you. Best of luck.