Many Characters from the Simpsons have made one-time appearances, but Many need to appear again. The list spreads looooooooooooooooooooooooooong, loooooooooooooooooooooooooooooong and looooooooooooooooooooooooooooooooooooooooooooooooooooonger. In this list we all Narrow it down, and only the truly best characters can win them all who have made questions unanswered
You are welcome to add more, and feel free to make ANY change you like, even copy and pasting
http://www.ranker.com/list/simpsons-one-time-characters-who-need-to-appear-again-vote-/r20x,
Hank Scorpio
Episode: You Only Move Twice (Season 8, 1996)
Hank Scorpio (Albert Brooks) is an evil genius. He is also the cheerful, friendly owner of Globex Corporation. Scorpio is considered by some to be Albert Brooks' best voice performance on The Simpsons and for this and four other guest performances he was named the greatest guest star in the show's history by IGN. Brooks ad-libbed many of his lines. Homer and his family never knew that Scorpio is an international criminal and they will never know about it. His name is a reference to Frank Serpico. He also appeared once in Simpsons Comics #117, "Sandwiches Are Forever", as well as Simpsons Comics #132,
Jacques
Episode: Life on the Fast Lane (Season 1, 1989)
Jacques (Albert Brooks) is a bowling instructor who pursued an affair with Marge Simpson. Jacques has since made non-speaking cameos in subsequent episodes, such as "Homer and Apu" (in the MonstroMart's line of single, pathetic men who only pay cash for their groceries and do not chat with the clerk) and "Homer's Triple Bypass" (in the waiting room with his bowling ball stuck on one of his fingers). He makes a quick appearance in the bowling team 'The Homewreckers' in "Team Homer" losing to Homer's bowling team the 'Pin Pals'. He is also seen being startled by Bart on his skateboard (along with Bleeding Gums Murphy, Barney, and Apu) in the opening credits of each episode (up until the middle of season 20, when the opening was changed for high-definition TV and the characters on the street were changed).
Don Brodka
Episode: Marge Be Not Proud (Season 7, 1995)
Don Brodka (Lawrence Tierney), chief of security at the local Try-N-Save store. Bans Bart for life from the store after Bart is caught shoplifting the Bonestorm video game.
Ronaldo
Episode: Blame it on Lisa (Season 13 ,2002)
Ronaldo (Tress MacNeille), a Brazilian orphan whom Lisa sponsors.
Tom
Episode: Brother From The Same Planet. Tom (Phil Hartman)
Donny
Episode: The Debarted (Season 19, 2008)
Donny (Topher Grace) is a new kid at school hired by Principal Skinner and Superintendent Chalmers to rat Bart out whenever he plays a prank at school. He resembles Topher Grace.
Guy Incognito
Alcatraz
Episode: Pranksta Rap (Season 16, 2005)
Alcatrazz (Hank Azaria), a rapper who lets Bart perform onstage.
Titania
Zachary Vaughn
Episode: Bart Gets a Z (Season 21, 2009)
Zachary Vaughn (Hank Azaria): Mrs. Krabappel's replacement teacher after Krabappel is fired (expelled) for drinking alcohol on the job.