Billy & Jimmy Lee

Billy Lee and Jimmy Lee are the two main characters in Double Dragon. They fight off against various gang members through the streets of a city and various other locations.

Appearance
Their appearances have changed throughout the life of the series, usually swapping between hair color. Billy Lee originally having brunette hair and darker skin and Jimmy Lee having Blonde hair and lighter skin. As the series went on in some games Billy's hair was changed to Blonde and Jimmy's to Brunette. Such titles as "Super Double Dragon" the twins' hair styles has changed as well having Billy with a brunette laid down style and Jimmy with a blonde high-cut style. In Double Dragon 2: The Revenge, Jimmy wears a white outfit instead of his trademark red outfit.

Gameplay
The gameplay in most of the games takes place in a pseudo 3D perspective like in Renegade and later beat-'em-ups, in which the player character can move in four directions but are always facing left or right. The player can perform a variety of unarmed fighting techniques against their enemies, as well use melee weapons such as baseball bats and throwing knives normally obtained from enemies. In some installments, there are techniques that can be done in combination with another player.

According to the supplementary materials for some of the games, Billy and Jimmy Lee practice the fictional art of Sōsetsuken (双截拳?, "Twin Intercepting Fists"), a nod to Bruce Lee's fighting method of Jeet Kune Do, meaning "Way of the Intercepting Fist". Some of the enemy characters take their names from Enter the Dragon such as Williams and Roper from the first game, as well as Bolo and Ohara in certain versions of Double Dragon II: The Revenge. Additionally, the packaging artwork of Double Dragon Advance is based on the climatic fight of the Bruce Lee film Return of the Dragon.

Double Dragon
Billy Lee, and/or his twin brother Jimmy Lee (also known as Hammer and Spike in the supplementary materials for the American arcade release) must fight their way into the turf of the Black Warriors gang in order to rescue their common love interest Marian.

Arcade Version
The game is divided into four different stages or "missions", which consist of a city slum, a factory, the woods, and the hideout of the boss. The game normally ends if a single player defeats the final boss alone. However, if two players manage to complete the game together then the two will be forced to fight each other in order to determine who will win Marian's affections.

NES Version
In this version, Jimmy Lee (the Player 2 character in the arcade version), serves as the main antagonist. After defeating Willy, the original final boss from the arcade game, Jimmy will appear before the player for the true final battle.

NES Story: Double Dragon is the story of Billy and Jimmy Lee, twin brothers who learned to fight on the cold, tough streets of their city. Their expert knowledge of the martial arts, combined with their street-smarts, has made them both formidable fighting machines.

But now Billy is faced with his greatest challenge: his girlfriend, Marian, has been kidnapped by the Black Warriors, the savage street gang of the mysterious Shadow Boss! Using whatever weapons come to hand - knives, whips, bats, rocks, oil drums, even dynamite - Billy must pursue the gang through the slums, factories, and wooded outskirts of the city to reach the hideout for his final confrontation with the Shadow Boss...his brother Jimmy!

Double Dragon II: The Revenge
Double Dragon II: The Revenge begins with Marian, the heroine from the original Double Dragon, being shot to death by the leader of the Black Warriors. Once again, the player assume the role of brothers Billy Lee and Jimmy Lee, who are now tasked with the duty of avenging Marian's death.

Arcade Version
Like in the original game, the arcade version of Double Dragon II is divided into four missions: a heliport, a lumber storehouse, a wheat field, and the new hideout of the boss. Each stage has its own boss character with his own leitmotif theme. After defeating Willy (the final boss from the original game) in the fourth stage, the player will confront a double of their own character for the game's final battle. If two players reach the end together, then both will get to face their own clone for the final battle.

The origin and identity of the clones are never revealed and they still remain mystery.

Nes/Famicom and PCE Version
There are three difficulty settings, which determine the length of the game (in the English version). The final mission is only available on the hardest difficulty setting. In this game Jimmy and Billy can be played simultaneously.

While the overall premise is the same as the arcade version, the game now features story sequences before each stage which serves to advance the plot. The level designs are also completely rearranged, with the NES and PCE versions featuring nine missions instead of just four. Most of the enemy characters from the arcade version are featured in the NES / PCE versions as well, while a few were replaced by new ones. Notably, the ninth and final mission is a battle against the Mysterious Warrior, a character introduced in the NES and PCE versions who serves as the new final boss. In contrast to the arcade's bittersweet ending, the NES and PCE versions features a happier ending in which Marian is brought back to life after the final opponent is defeated.

Double Dragon 3: The Rosetta Stone/The Sacred Stone
After returning home from a two-year training mission, Billy and Jimmy Lee come across a fortune teller named Hiruko. The woman tells the Lee brothers that in order to challenge the world's strongest adversary, they must seek out the three Rosetta Stones that have been scattered around the world.

The game begins in the United States, where the Lee brothers must defeat the remnants of the Black Warriors gang from the previous games before they set off to find the stones. Afterward, the heroes must travel to China, Japan and Italy, where each of the stones are being guarded by formidable fighters unique to each country (such as swordsmen in Japan and archers in Italy) who will refuse to give them up without a fight. Once all three Rosetta Stones have been procured, the Lee brothers' journey reaches its final destination in Egypt, where they face all sorts of supernatural creatures as they enter Cleopatra's tomb to uncover the mystery surrounding the stones.

Double Dragon IV
After the defeat of the Black Warriors in Double Dragon II, Billy and Jimmy Lee look to spread their Sōsetsuken martial art by establishing dojos around the country. However, they soon face a new threat in a gang called the Renegades operated by Okada Sisters who are looking to expand their criminal hegemony beyond Japan. Renegades have also teamed up with the Black Warrior remnants to put an end to Billy and Jimmy once and for all.