Touhou Mother

Touhou Mother is a fan-made crossover game of Touhou and EarthBound/MOTHER, made by 'S'.

Made in RPG Maker 2000, the game begins when a Meteor crashes into Gensokyo. After Reimu and Marisa fight of the mysterious alien that arrived with it, they find an unconscious boy nearby, who reveals that he has no memories. Soon after, things go to hell in Gensokyo. Not that that stops the lightheartedness and endless references to other works.

The translated game can be found here, while a playthrough can be found here. A sequel to the game, Return of Touhou Mother, is currently being uploaded as a series of videos by vgperson here.

Tropes used in Touhou Mother include:

Amnesiac Dissonance: When he first arrives, Porky has no memory of his past. Later, he pretends to to be this to mask the fact that he remembers everything.
And Now for Someone Completely Different: After Reimu, Marisa and Yuka are sent to Old Gensokyo, Sanae stars in her own chapter. She returns after Reimu collects the seventh melody.
Apologetic Attacker: Reisen.
Art Shift: The early designs for Reimu, Marisa and other cast members are used when they're in Old Gensokyo.
Big Damn Heroes: ...This happens a lot, let's just say that. It's subverted almost as often.
Break the Haughty: After the party defeats Future Badass Cirno, she's reduced to staring at the wall and muttering about how useless she thinks she is.
The Cavalry Arrives Late: Played with horribly near the climax, when everyone else shows up and mistakes the roboticised Reimu, Marisa and Tenshi for mere Mooks.
Changed My Mind, Kid: This is how Mima joins the party.
Chekhov's Gun: The Eight Melodies.
Clipped-Wing Angel: Tenshi gives Scarlet Weather Rhapsody of All Mankind a second try during her second fight... and the Rainbow Sword can't take it and snaps to pieces, which knocks her out.
Cold-Blooded Torture
The Dragon: Tenshi works against the heroes more than almost anyone else, effortlessly beats down Remilia and Yukari, and unlike the other Touhou characters is never persuaded to switch sides until the very end of the game, after Porky turns her into a robot to cover his escape.
Darker and Edgier: Especially on the take of the relationship between humans and youkai in Gensokyo.
Demoted to Extra: While the gameplay leans decidedly towards the MOTHER side of things, the characters from said series are for the most part pushed to the wayside.
- Not so on the sequel though.
Future Badass: A few characters become this after the party returns from Old Gensokyo.
Guest Star Party Member: Several, always filling a 'fifth' slot. These include Nitori, Sanae and Tenshi.
Gods Need Prayer Badly: Source of a fairly big Mood Whiplash in the sequel. En route to your next destination you happen upon Sanae and a very transparent Kanako. They explain that the incidents in the previous game caused a great many humans to no longer believe in or care about gods, so Kanako's physical being is vanishing from the world. And then when you return to that area later, neither Kanako nor Sanae are present.
Grey and Gray Morality: Are the humans justified in liberating themselves from the youkai they had feared for so long by merging Gensokyo with the Outside World? Or is it the youkai who are justified in keeping the humans under their thumb if it means preserving Gensokyo?
Fake-Out Fade-Out: Both times against Tenshi's final attack. The first time has Ridley's battle music, the second time has Bhava Agra As Seen Through A Child's Mind start back up at full force.
Fantastic Racism: One of the conflicts for the sequel, found near the end of Chapter 1. Porky was just the nudge needed for the humans and youkai to realize just how much they disliked each other.
Friendship Moment: Several between Marisa and Porky, until his Face Heel Turn.
Heel Face Turn: Eirin, Kaguya, and Kanako.
Heroic BSOD: Reimu and Marisa refuse to fight all of Gensokyo, mostly ignoring the player's input.
Hopeless Boss Fight: Several, but the worst comes right at the end, against all of Gensokyo.
Homage: Sanae's side of the story is a loving tribute to Metroid and Metal Gear Solid.
Karma Houdini: Unfortunately, Touhou Mother is set before Mother 3, meaning that Porky gets to escape justice. Considering the Cold-Blooded Torture she engaged in, Eirin is also Easily Forgiven.
- In Naka Teleeli's Let's Play, however...

NakaTeleeli: If I have to alter time-space itself...

Les Yay: Frequently teased.
Let's Play: Naka Teleeli has a blind run beginning here, where he points out many of the Shout Outs and references. Notably includes character 'cheat sheets' to help anyone unfamiliar with the Touhou series, and a quick summary of the events of the MOTHER series as an optional starting point.
Lightning Bruiser: Mima hits almost as hard as Yuka, is faster than Marisa and has some of the most powerful offensive and healing spells right from the beginning.
Medium Awareness: Marisa likes to make references to game mechanics, particularly the four-person party aspect.
Mighty Glacier: Yuka fills this role.
Mood Whiplash: In the vein of the Mother series.
Mushroom Samba: Mimicking Tanetane Island, of course.
My Human Village Right Or Wrong: Poor Keine...
Mythology Gag: Because of Phantasmagoria of Flower View, Yuka's speed never naturally increases.
The Obi-Wan: Mima invokes this in order to teach Marisa Starstorm.
One-Hit Wonder: Sanae, for a little while, anyway.
Recurring Traveler: S, appearing as a white Kirby, more or less.
Recurring Boss: "a", a slime who multiplies his stats by some number each time you fight him. Also Tenshi and Reisen, as New Reisen and Miracle Reisen.
Running Gag: Yuka and her (lack of) speed.
- "There are ants at your feet. ...What, here? Get back to the forest!"
- "Dude? That's rad."
Shipper on Deck: Mima seems to ship Marisa/anyone.
Shout-Out: So many that it's hard to know where to begin...
Silent Protagonist: Reimu has no written lines; Marisa and her other companions do most of the talking.
- Until the The Stinger at least.
Squishy Wizard: What else would you expect of Marisa?
The Revolution Will Not Be Civilized: The humans who want to rebel against the youkai's rule aren't portrayed in a positive light. After all, they are led by Porky and if they get what they want, Gensokyo will vanish as the consequence.
Time Skip: The sequel is set six months after the end of Touhou Mother. It Got Worse since then.
Took a Level in Badass: Cirno goes from goofy comic relief boss battle to one of the more difficult boss battles in the game sometime while the party is stuck in Old Gensokyo.
The Unfought: Porky, Eirin.
Unwilling Roboticisation: Happens to Sanae and poor Reisen, with the latter sticking better than the former.
- Near the climax, Reimu, Marisa and Tenshi are put into robotic bodies.
- In the sequel Yukari does this to Reimu, turning her into something similar to the Masked Man.
Technology Is Evil: One of the major conflicts is the forced modernization of Gensokyo.
The Quisling: When stuff starts going to hell in Gensokyo, Kanako, Tenshi, Eirin and Kaguya align themselves with Porky and the Pigmasks.
Well-Intentioned Extremist: Remilia tries to take over the human village to drive Porky out of Gensokyo. By bringing an army of undead there and killing everyone in it.
- The sequel has Yukari bring some of the most powerful youkai in Gensokyo together and forcefully takeing over, under the impression that should humans get any sort of power they will always abuse it.
  - Yukari is willing to do just about anything to protect Gensokyo. Even if it means becoming just like Porky.
Worthy Opponent: "a" considers you this by the end, healing you to full before the fight and giving you a strong weapon upon defeat.
What Happened to the Mouse?: Rinbokusan is stated to be on board Porky's ship. She never actually shows up.
What the Hell, Hero?: Marisa does most of the calling-out.
You Cannot Grasp the True Form: Unreasonable Guy... did something!