Kaeru no Tame ni Kane wa Naru

Since they were small children, the young Prince of Sable and Richard, the prince of the Custard Kingdom, were rivals in fencing. However, Richard always bested the prince of Sable, who dreamed to beat him some day. One day, word reaches that the Croakian Army, led by Lord Delarin, invaded the peaceful Mille-Feuille Kingdom and abducted Princess Tiramisu. Richard immediately sets out to save the kingdom, followed by the Prince of Sable. With that, an adventure begins to save the Mille-Feuille Kingdom and Princess Tiramisu.

And frogs. A lot of frogs.

For The Frog The Bell Tolls (original title: Kaeru no Tame ni Kane wa Naru) is an action-adventure/RPG hybrid for the Game Boy, developed by Nintendo. It was influenced by their own The Legend of Zelda series, which inherited some elements of this game. The later released Links Awakening shares an engine with it and has a cameo by Prince Richard in a house full of frogs. Since then, For the Frog the Bell Tolls hasn't gotten much acknowledgment by Nintendo, but Dr. Arewo Stein managed to appear as a recurring NPC in Wario Land 4, and there is a sticker of the Prince of Sable in Super Smash Bros. Brawl.

The game never got a release in America or Europe, but a complete fan translation exists.

Tropes used in Kaeru no Tame ni Kane wa Naru include:

Anticlimax Boss: Played with at the end. Lord Delarin appears as a simple snake, which the Prince lampshades. But before the Prince can kill him, Delarin transforms into a huge snake.
Bag of Spilling: The prince begins the game filthy rich, but loses it due to unconcerned spending and thievery. He gets the stolen money back, but loses all his money again, to buy a potion that turns him back to a human.
Baleful Polymorph: Initially, the potion of Mandola turns the prince, Richard and the entire Custard Army into frogs. Later, the prince can change forms and even turn into a snake willfully.
Big Damn Heroes: The final battle is full of this.
Big Ball of Violence: How battles are done in this game.
Big WHAAT?!: The Prince, frequently.
Bland-Name Product: Nantendo, who apparently make strength-enhancing wristbands. Considering who made this game, it's doubtful that there were any legal reasons for this.
Bribing Your Way to Victory: After a boat-owner lays down the law to Sable, Sable offers a small sum of coins to bribe his way to scene of the princess' abduction.
The Cameo: Shigesato Itoi mining for gold. No, really.
Chekhov's Gun: The stuff Dr. Arewo Stein is working on when he gives a upgrade to the Prince.
Damsel in Distress: The princes think Princess Tiramisu is this, but then find out that no one knows where she is.
Dronejam: Frogs and snakes with "bad attitudes" block some paths.
Emergency Energy Tank: Wine.
Experience Points: Averted, the player has to find certain stones that raise his stats directly.
Eye Scream: Lord Delarin gets a sword thrown on his eye during the final battle.
Frogs and Toads: As the name suggests, frogs play a rather big part in the game. Including Baleful Polymorph.
Heart Container: Or rather "Heart Stones".
Hearts Are Health
Hello, Insert Name Here: The player gets to name the prince of Sable.
Heroic Mime: Averted. The Prince might not have a canon name, but he does have a voice.
Hopeless Boss Fight: The Prince can't win against the mammoth. He then resorts to mind control.
Hyperactive Metabolism: Wine, and even bugs when he is a frog, regains the prince's health.
Idiot Hero: The Prince of Sable.
The Maze: The way to the witch Mandola on Mt. Bavarian. Thankfully, the way is described on a sign near the entrance.
Money Spider
No Export for You
Pointed Ears: The witch Mandola.
Point of No Return: Lord Delarin's throne room.
Prop Recycling: Some sprites and sound effects are reused in Links Awakening.
Reptiles Are Abhorrent: Lord Delarin, the leader of the Croakian Army, is a snake.
The Rival: Prince Richard.
RPG Elements
Running Gag: The Prince continuously loses and regains a large amount of money over the course of the game. However, it's never around when you can use it to shop.
Schizo-Tech: On the surface it's a generic fantasy world with Medieval Stasis, but there are modern-day corporate buildings, among other things.
Shout-Out: After he finishes the maze on Mt. Bavarian, the Prince of Sable remarks that he saw the trick before somewhere.
Side View: The dungeon levels are mostly made of such segments.
Spikes of Doom: Small spikes deal little damage. Big ones kill in one hit.
Theme Naming: Some places and characters are named after sweets.
Top Down View: The usual view, aside from the Side View segments.
Unexpected Gameplay Change: the final part of the battle against Lord Delarin.
Wicked Witch: Mandola.