From the time I began with M&L sprites, many people have told me I should throw together some sort of fan-game with all the work I've done. I eventually decided that was a good idea, and after dragging it along by myself for a while, Starpower joined so we could have our sprite collab and Phaze hopes to be coding the engine from scratch, along with TheShyGuy who is implementing features specifically for this project into his Animation GUI.
Aside from this, we love Mario games, and this is our tribute! As for myself, I've always been a believer that Nintendo makes a lot of Mario characters and settings that never get reused but have lots of potential, so this is my way of integrating the universe into something tangible while adding some original ideas.
This fan-game is also an attempt to non-intrusively add fan-content and characters to an existing game universe where Mario himself is not the main focus without the general idea being off-putting. Yeah, that's the plan.

-Opening and Tatanga's Plan-
Ridge the Koopa, Bloopregard the Blooper, Le Bou the Boo Balloon, Cole the Frost Ptooie, Bullit the Snifit, and Flora the Flutter awaken in an unknown base. They eventually learn that they've been abducted by Tatanga and his new army as guinea pigs for a prototype potion called Pleorax, developed by the Tatangang's chemist Kamest the Magikoopa. Pleorax is meant to unlock superior abilities within the drinker which under normal circumstances would be unattainable.
The six characters manage use their abilities to make their way past the base's security. They are then engaged by Despir the Arachne, Tatanga's right-hand man, and upon defeating him in a tutorial battle, they escape the base via a portal. Tatanga and Despir decide to send Turk the Chomp Bro. and K. Ramble the Kritter to follow the escapees. This pair bother the playable cast at various points throughout the story and act as comic relief.
After organizing his observations of Ridge and company, Kamest reports to Tatanga that in order to trigger the effects of Pleorax, the individual must come into contact with his or her opposite element (Fire/Ice, Water/Mechanical, Ground/Air, Light/Dark). Tatanga prepares his alien troops be given Pleorax and to move their invasion plan to the next phase.

-Central Plot-
Upon their return to the Mushroom World, Bullit reveals he stole a golden pocketwatch case from the Tatangang Base. Overhearing this discovery, Katsini, a magician bearing a striking resemblance to Tatanga, promptly challenges them to a duel. Afterwards, convinced of their skill, he explains that they'll need to seal the scattered pieces of the Tempest Timekeeper, a pocketwatch which can alter the balance of the elements, within the case they hold. Despite Ridge and company's unanswered questions, however, he vanishes.
After relying on their own intuition, the six friends ultimately discover that each of the Timekeeper pieces is guarded by a Mushroom World magician. Due to Tatanga's recent meddling, each piece begins to cause elemental anomalies in its respective region; in line with this, each of the six playable characters begins to lose his or her sanity and goes missing, furthering their motivation to find the rest of the Timekeeper. To obtain each piece and restore its balance to normal they clear the area's obstacles, battle native enemies, and defend against Tatanga's alien troops, which have invaded via UFOs perched atop Mushroom World monuments.
During their journey, Ridge and company are also plagued by a mysterious gang of four black shapeshifters of unknown origin. They do not speak and appear not to have any affiliation with the Tatangang, but have a strong affinity with the elements and eventually make it apparent that they're after the Timekeeper pieces as well.

In this respect, A Koopa's Tail draws inspiration from all four Mario & Luigi titles. Unlike any of those, however, it introduces a drastically different party system, abilities, and more.

1. General
   • Any two of the six playable characters may be present at one time in Overworld and Battle.
     
2. Overworld
   • In addition to traveling, character abilities can be used to solve puzzles. Each character has a Jump command, two abilities, and a Team move.
     
   • Obtain items and badges, complete sidequests.
     
   • Dialogue and cutscenes. HUD overlays are disabled during these instances.
     
   • Encounter enemies and bosses. Running into or attacking an enemy triggers battle mode; items obtained in overworld may be used in battle.
     
3. Battle
   • Fighting enemies and bosses.
     
   • Stats include HP, SP, POW, DEF, SPEED, and TEAM. Team is the equivalent of 'Stache from BIS.
     
   • Badges return as a new line of Team-based equips, a combination between BIS and TTYD. Each character may equip only one which can be swapped out in Battle without costing a turn.
     
   • Each character has up to four solo abilities which use various types of action commands. The first two moves are standard offensive, while the latter two are more advanced and require Special Points to use.
     
   • Each character can use a Team Move, which require SP to use. The first half of the attack's action command remains constant to the partner who uses it; the second half varies depending on the other party member present.
     
   • Shield and counter enemy attacks.
     
   • Party leveling system: all characters level up simultaneously once a certain EXP is reached. Each sequential level-up requires more EXP to reach.
     
   • Enemies may drop coins or spoils upon being defeated.
     
   • When selecting an action, all HUD overlays are visible. When attacking, guarding, or using items, HUD elements disappear.
     
4. Abilities List (Team Moves TBA)

   • --Overworld-- (All characters have a universal Jump command)
     -Ridge-
     Shell Shot - Squeezes through tight spaces and retrieves items
     Spikeblade - Travels faster and climbs walls
     
     -Bloopregard-
     Bowler Bung - Throws his hat like a boomerang, can cut through objects
     Piggyback - Swims over various terrain
     
     -Bullit-
     Bill Blast - Twin Bullet Bill shot to hit switches
     Recoil Jump - Launches stories into the air where others can't go
     
     -Flora-
     Windy Wings - Move far-away objects or turn propellors
     Glide - Carries the other character or objects over gaps
     
     -Cole-
     Chill Chomp - Bites onto objects, the other partner can pull him
     Frostpectorate - Spits a hunk of ice to create or freeze platforms
     
     -Le Bou-
     Terror Tongue - Create vibrations with a cackle to trip alarms and more
     Outta Sight - Access hidden areas by turning intangible
     
     --Battle--
     -Ridge-
     Beak Bash - Smashes with his beak, much like M&L's Hammer
     Shell Toss - Throws his shell
     Spikeblade - Saws along the ground at high speed
     Gravel Grind - Digs into the ground with the Spikeblade, kicking up rocks and boulders
     
     -Cole-
     Chill Chomp - A frosty bite
     Frostpectorate - Spits a hunk of ice
     Freezer Burn - Freezing breath that affects all enemies
     Icicle Drop - Exhales ice particles into the air, forming a giant icicle
     
     -Bloopregard-
     Torpedo Tackle - Propels himself forward head-first
     Bowler Bung - Throws his hat like a boomerang
     Inky Emission - Spews ink to confuse enemies
     Tentacle Gyration - Twirls his tentacles like a drill and bounces until a command is missed
     
     -Le Bou-
     Terror Tongue - A high-pitched cackle followed by a lick
     Party Popper - Pops like a balloon, much like a Bob-Omb's explosion
     Deflate - Sucks in air and propels himself forward, ricochets until a command is missed
     Outta Sight - Avoid attacks with the other partner in the shadows
     
     -Bullit-
     Tackle - Throws himself forward shoulder-first
     Bill Blast - A twin shot from his Blasters
     Recoil Jump - Launches into the air using his cannons and crashes down with great force
     Bomb Barrage - Dispenses bombs which explode after a few turns
     
     -Flora-
     Windy Wings - Stirs up a stong gust to damage or blow enemies from battle
     Flutter Fury - A barrage of physical attacks
     Tool Toss - Throws a tool corresponding to the action command
     Seed Summon - Seeds grow into various plant species which either attack enemies or help the party
     
     --Pleorax-- (Includes all original abilities)
     Ridge (Ground): Air - Gargantuan Koopa Troopa
     Cole (Ice): Fire - Bramble & Bungee Piranha
     Le Bou (Darkness): Shapeshifting via Balloon Animals
     Flora (Light): Dark - Creates strong storms with her wings
     Bloopregard (Water): Electricity - Electro-Blooper
     Bullit (Metal): Water - Spits Bullit Bills, Zeus Flamethrower
5. Pleorax Battle
   • Solo battles between the affected party member and a boss.
     
   • Party members, if present, may act as assists.
     
6. Mini-Games
   • Mini-games are triggered in overworld but use various rooms, moves, and commands.
     
   • Most are plot-specific, some are part of sidequests.
     

Tatangang Base (A Koopa's Tail)
Neuron Jungle (Yoshi's Story)
Yoshi Village (Yoshi's Island, Mario & Luigi: Partners in Time)
Pipe Vault (Super Mario RPG)
Toad Town (Mario & Luigi: Bowser's Inside Story)
Star Hill (Paper Mario, Mario & Luigi: Partners in Time)
Mushroom City (Mario Kart: Double Dash!!)
Mushroom City Underground (A Koopa's Tail)
Shy Guy's Toy Box (Paper Mario)
There are more but we're avoiding spoilers!

Character Artwork
[spoiler=Le Bou]