“The Green Thunder strikes like lightning!”
Mr. L, also known as The Green Thunder, is Luigi's brainwashed counterpart, who makes his appearance in Super Paper Mario, serving as an acolyte of the evil Count Bleck. According to The InterNed, Mr. L's theme song is titled "Mr. L, Green Thunder". Eventually he became the secondary antagonist of the game when he became Super Dimentio.
 Super Paper Mario
 In the Light and Dark Prognosticuses
It is implied several times that Mr. L/Luigi is the "man in green" referenced in both the Light Prognosticus and the Dark Prognosticus, both of which state that this man in green and his affiliations will determine which prophecy is true. As such, it can be taken that, if Luigi were to have stayed Mr. L throughout the course of the game, the Dark Prognosticus would have been fulfilled and all worlds would be destroyed, making the end of Luigi's hypnotizing and evil ways integral to Super Paper Mario. Dimentio additionally states that the Dark Prognosticus mentions Luigi as the ideal host for the Chaos Heart.
 Early History (as Luigi)
An unconscious Luigi (who had not yet become Mr. L) is seen among the audience of Bowser and Princess Peach's wedding in Castle Bleck's wedding hall. As Luigi gains consciousness during this forced marriage, he attempts at saving Princess Peach from the clutches of Count Bleck and associates, but ends up only provoking the Chaos Heart (which was secured by an escaping Count Bleck shortly after).
Luigi is soon warped to a corridor of Castle Bleck. He meets a pair of Goombas (one of which was Gary) that tricks him into helping them escape the castle. Luigi makes an attempt at saving his group and Peach, but ends up coming to a dead end, where he is promptly surrounded by Nastasia's forces (as well as his two Goomba "friends", who joins Count Bleck, one by will and the other through hypnosis). Though Luigi's fate is not explicitly given, he is shown to be tackled by the troopers and is seemingly about to be hypnotized by Nastasia (foreshadowing Mr. L) just as the scene cut.
 Encounters with the Heroes and Other In-Game Events
Mr. L himself is first seen in the Whoa Zone, where he jumps on Squirps in a room before the statue of Squirpina XIV and the resting place of Outer Space's Pure Heart. After quickly trash-talking the three heroes, he engages them in a brief mini-boss battle with them. During this battle, he is able to heal himself using Shroom Shakes, but the heroes can use Thoreau to steal these shakes for themselves. After his 40 Heart Points are depleted, Mr. L falls to the ground and compliments the heroes on their battle skills, but quickly summons his mechanical "brother", Brobot, to finish them off. With the effect of the screen ripping in half, the characters are all transported to the depths of space, where Mr. L and Brobot battle them above what flipping would reveal to be a green, vector-graphic-filled mountainous expanse. Using Squirps's Squirp Squirt Beam, the heroes knock Mr. L out of the skies and the villain plummets back down to the ground. With one last boast of a future ability to prevail over the heroes, Mr. L escapes, allowing them to obtain the Pure Heart.
Mr. L next appears in the Castle Bleck intermission after Chapter 4, the beginning of which focuses on his "new-minion orientation." Mr. L is shown here to be boastful even around fellow minions of Count Bleck, seeing his comrades as weaklings and "junior minions". O'Chunks and Mimi react negatively to this, with Mimi noting to Mr. L that he too, had been, defeated; Mr. L's response is that he was "merely scouting" Mario, and would soon defeat him. With a cry of "L-ater!", Mr. L jumps off to Castle Bleck's unseen repair bay as Count Bleck quotes a Dark Prognosticus section stating the potential of the man in green.
In the intermission after King Croacus IV's defeat, Mr. L expresses a longing to make another attempt at destroying the heroes with his newly-repaired and improved Brobot. However, Nastasia relays a command from Count Bleck for the minions not to attack, and Mr. L thus could not carry out his plans. Mr.L then proceeds to whine, until Dimentio, encouraging the fulfillment of his own gambit, appears and convinces Mr. L and Mimi to attack anyway in saying that Count Bleck would be pleased if they were to end the heroes games.
As laid out, Mr. L encounters the heroes once again in the destroyed form of Sammer's Kingdom, where he takes the stone Pure Heart of Sammer's Kingdom for himself and engages the heroes in battle along with his improved Brobot. He loses this battle to the heroes and flees, leaving the broken Pure Heart to be obtained by them.
After Mario's team leaves the World of Nothing, Mr. L is shown in a cutscene where he ponders his inability to beat the heroes to himself. Shortly afterward, Dimentio appears, attempting to destroy him on the apparent basis that he, having lost once more, would be unable to show his face to Count Bleck (In actuality, Dimentio plans to undo Mr. L's hypnotism and reunite Luigi with Mario so they could help him destroy Count Bleck; he also uses his ambiguous help to Mario as a basis to convince him to join him in the battle against Bleck). Dimentio successfully destroys Mr. L, sending him to The Underwhere.
 Super Dimentio
By destroying him, Dimentio cures Mr. L of Nastasia's hypnosis and reunites him with Mario (at which point Mr. L's theme plays). Luigi joins the heroes in their quest, fighting alongside Mario, Princess Peach, and Bowser, who are eventually able to defeat Count Bleck. However, prior to this momentous victory, Dimentio had planted a Floro Sprout seed in Luigi's mind that grows into an adult Sprout, just as he is ready to finish the remaining three heroes off so he can destroy all worlds and create his new ones. Though Luigi notices and resists his brainwashing, his fate is imminent: Just as Nastasia once had, Dimentio creates Mr. L.
Making way for a new creation, Dimentio orders Mr. L to move into position and merges him with the Chaos Heart in a purplish-black hole resembling the Void. While one with the evil heart, Mr. L becomes the more Dimentio-themed Super Dimentio, a gigantic clown-like puppet bearing some resemblance to a twisted Luigi. Seemingly eliminating the new Mr. L's sentience, Dimentio takes control of Super Dimentio, challenging the remaining heroes. With help from Count Bleck and his minions, the heroes are able to summon the Pure Hearts to destroy Dimentio and the Chaos Heart, bring back Luigi and apparently finally erase his hypnosis and brainwashing.
Mr. L's only appearance beside his large role in Super Paper Mario is a passing mention (under the name Mister L) in Paper Luigi's trophy in Super Smash Bros. Brawl. This one-sentence mention states that Luigi only has a rumored "close relationship" to Mr. L and misattributes Luigi's brainwashing to Count Bleck. However, this could have been intentionally done to not spoil the ending, as Mr. L is not revealed to be Luigi until the end of the game.
 General information
 Physical appearance
Mr. L strongly resembles Luigi, though he is dressed in a black jumpsuit that strangely retains his former overalls' large buttons. He also wears a green bandanna around his neck. His new cap is similar to his old one except with a black background and reversed "L." Over his face is a small, black mask which seems to effectively hide his identity; this mask makes his eyes and eyebrows appear white. His gloves are dark gray and his shoes are black and Mr. L, unlike standard Luigi, is shown to have a belt.
It may also be worthy of note that official artwork depicts Mr. L's mustache as black whereas Luigi's Super Paper Mario artwork gives him a brown mustache. In game, however, both forms' mustaches are brown.
While it is somewhat obvious that Mr. L is a brainwashed Luigi to the Player, the other characters in Super Paper Mario don't make the connection, though they do feel like they know him in some way. This is done for both comic relief, and to facilitate the game's developing storylines.
A gentleman thief, Mr. L is very cocky and is always praising up himself, a stark contrast to the chicken-hearted, reluctant Luigi. He thinks highly of himself and is not slow to reveal it, often trying to openly annoy other in-game characters. He has a sophomoric belief in his often-boasted-of abilities, as he is very shocked at his failures as their series begins. He is very daring, and as such reveals an attraction to Princess Peach and jealousy of Mario's jumping ability. His loyalty to Count Bleck, while very deep (with him greatly longing to impress the count), is never explained, and he seems to care little about the expenses worlds would pay had Bleck's plans realized.
Mr. L has two catchphrases: "L-ater," which he continuously proclaims when exiting Castle Bleck, and "Have at you!", his battle cry. He has become well-known for his introduction (actually done only once in the game, not counting a shortened version featured in his new-minion orientation), in which he is given a repeated, blurring closeup as he spins around and strikes a pose, shouting "MR. L!" as rotating green rays are emitted from his body. He also has a knack for nicknaming, referring to Mario as "Mr. Jumpsallthetime," Peach as "Ms. Alwaysgetskidnapped," or Bowser as "Mr. Getsfoiledallthetimebytheredguywiththemoustache" during their first confrontation which may imply that he still retains some of his memory from while he was Luigi as he subconsciously recognizes who Mario, Peach, and Bowser are. He also nicknamed himself "the Green Thunder".
Dimentio's Mr. L seems to have no personality differences from Luigi, if he can be said to have any personality at all. Super Dimentio, however, he does give a few of Mr. L's cries, such as "GREEEEEEN!" and "L-POWER!".
 Powers and abilities
Mr. L's abilities are largely the same as those of Luigi. He runs and jumps around, not unlike a playable character and can also Super Jump, a trademark move of Luigi's in Super Paper Mario. Also hero-like is his ability to revive his health with up to three Shroom Shakes.
However, Mr. L has some skills that Luigi doesn't, namely his inventiveness. Though Luigi has been known to have run a mechanical-themed board in the Mario Party series, his mechanical skills haven't been consistently shown to match that of Mr. L. As aforementioned, Mr. L builds, upgrades, and pilots his own Brobot mech throughout the course of Super Paper Mario, pioneering the art he refers to as brobotics.
First Battle: "That's Mr. L. This new hire of Count Bleck's a real mystery man... Max HP is 40. Attack is 3. He uses his high jump as a weapon... And that powered-up super jump is quite...super... He has no other outstanding features of note. And why does he remind me so much of Mario...?"
Brobot: "That's the Brobot. This super robot is one of Mr. L's creations... Max HP is 255. Defense is 3. Defense against fire is 6. It is loaded with different weapons that allow it to attack from any angle... Just try to avoid its attacks and use Squirps's beam when you get a chance... And try to grab a few Choco-Bars that float by..."
Brobot L-Type: "That's Brobot L-Type. Mr. L pulled out all the stops to make this one... Max HP is 64. Attack is 5. Defense is 4. Defense against fire is 8. Most of its moves are the same, but it can now use its hands or tackle you... He seems to be weak to explosions, so try using Boomer on his feet... You remember that after setting a bomb, you can press 1 again to set it off, right?"
Super Dimentio: "That's Super Dimentio, a freakish blend of Dimentio, the Chaos Heart, and Luigi. That monstrous body has immense power... Max HP is 200. Attack is 6. Concentrate attacks to the head. You'll have to climb those platforms to reach the head to attack. This is truly the final battle... Winning is the only option..."
 Names in other languages