Walker

Walker is the vigilante warden of the large prison in the Ghost Zone, where he imprisons the inhabitants for minor offenses.

Prisoners of Love
Walker was a ghost that lead the Ghost Zone police, arresting any ghost that broke any of "the rules", however he often imprisoned them harshly for very minor offenses. He first encountered Danny Phantom after the half-ghost accidentally drove his father's new Specter Speeder into the Ghost Zone. Walker told Danny that if he ever came into his jurisdiction again, he would lock him away. However the half-ghost was forced to enter the Ghost Zone again to retrieve a present for his mom that he'd accidentally send there. Danny found the present, but was captured by Walker and his Ghost Guards for possessing human world contraband. He imprisoned the half-ghost along with many of the ghosts he'd battled earlier, but Danny managed to get them to put their differences aside. They organized a riot and the other ghosts succeeded in escaping while the half-ghost went to confront Walker so as to get the present back. At first, Danny was unable to take on the warden ghost, but he realized that humans in the ghost zone had the same qualities as ghost in the human world, meaning they could pass through objects. He turned back into his human form and retrieved the present, then headed back to the human world with Walker proving unable to lay a hand on Danny.

Public Enemies
However Danny hadn't heard the last of Walker and he plotted to turn all of Amity Park against the half-ghost. He used Wulf, one of his inmates with the ability to follow scents and tear open portals to the human world, to get his army of Ghost Guards to the town. Walker had them attack the town to raise panic, then he and his minions began to possess people around Danny, personally taking control over Dash Baxter. Eventually he took control of the mayor and planned to have Jack Fenton put in charge of ghost defense, who would leave the town helpless due to his incompetence. But Walker was defeated by Danny with help from Wulf and he and his Ghost Guards were driven back into the Ghost Zone. But despite being defeated, Walker's plans nonetheless succeeded to some extent, causing Danny's reputation amongst the people to be negative making Danny Amity Park's Public Enemy #1.

The Fright Before Christmas
Walker was attending a Christmas party with various other ghosts when Danny showed up, having been sent there by the Ghost Writer. At first, the half-ghost was confused by why the ghosts were so welcoming, but then Walker and the others explained the Christmas Truce and how it said ghosts were forbidden to fight on Christmas, with the ghost warden even saying that it was one of "the rules". When Danny told Walker and the others that the Ghost Writer was violating the truce, they were outraged and went with him to confront the writer. But though the Ghost Writer used his powers to make them fight each other, Danny broke his spell by picking up an orange since nothing rhymed with orange. Walker had his Ghost Guards imprison the Ghost Writer and was seen offering him an orange, which greatly frightened the writer.

Claw of the Wild
Walker and his minions were pursuing Wulf and some other ghostly monsters that had escaped the Ghost Zone through a portal the wolf ghost had created. However when they found out Danny was at a nearby summer camp, they abducted the other campers so as to use them as bait for the half-ghost. Walker sent his Ghost Guards to give Danny a message, bring him Wulf, who he'd found, in exchange for the release of his friends. However Sam dressed up in a costume to fool the ghost warden into thinking she was Wulf and they managed to rescue everyone, as well as defeat Walker once again.

Phantom Planet
Walker was amongst the countless horde of ghosts that helped Danny turn the entire planet intangible so as to save it from the Disasteroid, thus saving the Ghost Zone as well.

Personality
Walker is extremely strict and a stickler for his rules in the Ghost zone. He always seeks to punish those who defy him and his minions. He commands his prison and minions with an iron fist and goes to whatever measures he takes in order to preserve order, even making up laws as he goes along. He uses these rules as excuses to do whatever he pleases. Unlike most of Danny's foes, Walker hardly ever leaves the Ghost Zone. His direct interference with the real world is minimal, as he usually has his minions to do his dirty work. He also prefers using his minions instead of straightly attacking his opponents, though he will fight them if necessary. Walker seems to be a consequentialist, getting really low on his means for the sole reason of preserving his rules, or to get revenge on enemies such as Danny or Wulf. He is shown to have some spiteful sense of humor, always making brief jokes as he proceeds with his plans, especially in later episodes. He also shows signs of being a coward by having Wulf wear an electrical collar and almost putting the collar on Sam.

Powers

 * Intangibility: Standard ghost power.
 * Invisibility: Standard ghost power.
 * Flight: Standard ghost power.
 * Size Alteration: He can grow his body to giant size.
 * Overshadowing: He used this power to possess the mayor of Amity Park to capture Danny in "Public Enemies."
 * Teleportation: He transforms into a green mist when teleporting.
 * Supernatural Strength: He can lift and throw Danny with ease.
 * Ghost Ray: He can fire pink ghost rays from his hands.

Abilities

 * Multilingual: Walker has some knowledge of Esperanto, as he is able to understand Wulf.

Weapons

 * Ecto-Rope Shooting Cane: A small cane that shoots a ghost ray that ties up any ghost. He and his minions use these.

Trivia

 * The southern accent that Walker bore might indicate that he might be from the southern part of the USA.
 * His white suit and black fedora hat could represent him being a sheriff or prison warden in the early to mid 1900s, or being a member of a mafia. It is possible, though unlikely, that he could be both.
 * The character is likely a nod to the long-running television series Walker: Texas Ranger.
 * Walker is the only ghost to ever catch Danny inside the Fenton Thermos.
 * Walker is one of the few ghosts that has never been seen being caught in the Fenton Thermos.