Kennedy (Japanese: クãƒãƒ€ Kuroda) is a character of the day in Stairway to Devon. He is voiced by Michael Sinterniklaas in English and Katsuyuki Konishi in Japanese. Kennedy is President Stone's assistant and is often found hunting his rogue charge down more times than not. Max mistook him for a kidnapper. Bulbapedia
Brodie was a member of Team Magma before its dissolution, after which he became known as "Brodie The Phantom Thief". He is also known as "The Man of a Thousand Faces," having perfected the art of disguising himself in order to get his goals accomplished. He debuted in the episode Unfair Weather Friends, disguised as Millie, a scientist at the Weather Institute who was supposed to be collecting data on Groudon. Team Aqua tried to steal the data directly, unaware Millie was really Brodie. When Shelly threatened to harm Bart and the other scientists at the Institute, Brodie revealed himself as a Magma agent and escaped with the information the Institute had gathered on the legendary Pokémon. Brodie also appeared in The Ribbon Cup Caper. He disguised himself as various people, including Officer Jenny, in order to steal the Ribbon Cup for the Hoenn Grand Festival. When confronted by the real Officer Jenny, Brodie willingly gave up the Ribbon Cup and flew away once again. He hasn't been seen since.
Watt is the assistant to Wattson. His name comes from "watt", which is a measure of electrical energy. He has appeared in two episodes of the anime. His first appearance was in Watt's with Wattson?. He more or less stood aside and let Wattson do everything, although he did serve as the referee in Ash's gym battle for the Dynamo Badge. When Ash and the others returned in Manectric Charge, Watt was featured much more prominently. He battled May and her Skitty with his Ampharos. Skitty proved to be stronger and defeated Watt's Electric-type. Watt was also the one to inform May about the Pokémon Contest in Verdanturf Town.
He lives on the Abandoned Ship, searching for his Marshtomp after he accidentally dropped its Poké Ball there many years ago. As it turned out, it evolved into a Swampert which attacked any intruders on the ship. When the Swampert realized that Tommy was its rightful owner, it rejoined him and both Trainer and Pokémon were a team once again. Tommy helped Ash and friends to get to Slateport City with his boat.
In Having a Wailord of a Time, Stephanie was going to select her first Pokémon from Nurse Joy in Slateport City. However, while Ash, Brock and Max were guarding the starters, the Torchic became impatient, and began running around the Pokémon Center. Eventually, all the excitement caused Torchic to evolve into a Combusken. Initially, Ash and the others were going to hide the Combusken and use May's Torchic as a diversion so it would seem like nothing would happen. But, fearing Stephanie would choose Torchic, they confessed to Nurse Joy what had happened. Nurse Joy told Stephanie that Combusken would probably be a bad Pokémon for a beginning trainer to use, so she chose Mudkip. Then Stephanie's father looked into the Treecko's eyes and fell in love with it. Nurse Joy allowed Stephanie's father to bring the Treecko with him, and she decided to keep the Combusken with her at the Pokémon center. In the Japanese version, she was never given a name. She was only referred to as "Girl" in the credits. Her English name, therefore, likely was inspired by her voice actress' name. Bulbapedia
Robert is a Pokémon Coordinator and has appeared in several episodes. He first appeared in Win, Lose or Drew, competing in the Slateport City Contest. He defeated Drew with his Milotic and won that city's ribbon. The next time Robert appeared was during the Hoenn Grand Festival. In Deceit and Assist, he was seen during the Appeals round using his Milotic. In the following episode, Rhapsody in Drew, he nearly became a victim of Team Rocket when they tried to steal his Contest Pass and his Pokémon. Ash tried to stop them using his Snorunt, but it couldn't get its Ice Beam to work. Robert took Snorunt aside and told it to concentrate more. Snorunt did, and thanks in part to Robert's pep talk, it evolved into Glalie. Robert then proceeded to the finals of the Grand Festival, which he won, and earned the Ribbon Cup. According to Drew, immediately after he won, Robert began training for the next Grand Festival. Bulbapedia
Marius (Japanese: ヨウスケ YÅ�suke) is the character of the day in The Spheal of Approval. Marius made himself the self-appointed security guard of the Oceanic Museum. He became angry with Max for trying to get into the museum when it was closed. He believed that him and Ash were thieves so he sent his Spheal out to attack them. Fortunately for them, but unfortunately for Marius, Spheal wasn't interested in battling and only wanted to play. When it finally listened to what Marius said and attacked, it got zapped by Pikachu's Thunderbolt. Marius was in utter shock think that it was impossible for a Pikachu to beat Spheal. Max goes on to explain that Water-types are weak against Electric-type moves. Soon Captain Stern enters the scene and Marius tells him that Ash and Max were thieves. Max then explains that he just wanted to see the museum. Afterwards, Captain Stern invited them all in to see the museum. Marius displayed his lack of knowledge about Pokémon whilst in the museum. He said he wanted to catch a Goldeen so that he could "evolve it to Gyarados". Ash then corrects him saying that only Magikarp evolve into Gyarados. Marius also dreamed about traveling around the world by sea inside the submarine that the captain was building. Soon he, Ash, and Max, are captured by Team Rocket, and then they come to find out that Team Magma stole the meteorite that Captain Stern was going to study. Marius tries to use his Spheal to save them but again it won't listen to him. After they chase down Team Magma, Captain Stern tells Marius and Max to go back to town to get Officer Jenny. They were able to get there in no time because of Spheal's incredible speed in the water. Later on, they find out that Team Magma got away with the meteorite. Thankfully, Captain Stern did have a small piece of it left. Marius told Ash that he wanted to have a rematch with him the next time they met. Bulbapedia