SpongeBob SquarePants (season 1)
The first season of the American animated television sitcom "SpongeBob SquarePants", created by former marine biologist and animator Stephen Hillenburg, aired from May 1, 1999 to April 8, 2000, and consists of 20 episodes.
 The series chronicles the exploits and adventures of the title character and his various friends in the fictional underwater city of Bikini Bottom.
 The show features the voices of Tom Kenny, Bill Fagerbakke, Rodger Bumpass, Clancy Brown, Mr. Lawrence, Jill Talley, Carolyn Lawrence, Mary Jo Catlett, and Lori Alan.
 Among the first guest stars to appear on the show were Ernest Borgnine and Tim Conway voicing the superhero characters of Mermaid Man and Barnacle Boy, respectively.
Mermaid Man and Barnacle Boy
Mermaid Man and Barnacle Boy are fictional superheroes in the Nickelodeon animated television series "SpongeBob SquarePants".
 Mermaid Man was voiced by Ernest Borgnine from 1999 to his death in 2012, and Barnacle Boy is voiced by Tim Conway.
 Mermaid Man and Barnacle Boy were created and designed by Stephen Hillenburg.
 The characters debuted on August 21, 1999 in the series' episode "Mermaid Man and Barnacle Boy".
SpongeBob SquarePants: Original Theme Highlights
SpongeBob SquarePants: Original Theme Highlights is the first album of songs played on the Nickelodeon TV series "SpongeBob SquarePants".
 It includes tracks sung by the cartoon's characters: SpongeBob SquarePants, Sandy Cheeks, Patrick Star, Squidward Tentacles, and Plankton.
 Its total running time is 9 minutes and 9 seconds, spanning seven tracks.
SpongeBob SquarePants 4-D
SpongeBob SquarePants 4-D (also known as SpongeBob SquarePants 4-D Ride, SpongeBob SquarePants: The Ride or SpongeBob SquarePants 3-D) is a cel-shaded 4-D film based upon the popular television series "SpongeBob SquarePants".
 It can be found at many aquariums and theme parks across the world.
 The ride consists of a pre-show which then leads into a stadium seated auditorium.
 The ride is in 4-D, meaning it is a motion simulator with a 3D movie.
 The effects on the ride vary at different parks.
 Water spray, bubbles, wind, leg ticklers, smoke, and smells are usually found.
List of SpongeBob SquarePants guest stars
In addition to the show's regular cast of voice actors, guest stars have been featured on "SpongeBob SquarePants", an American animated television series created by marine biologist and animator Stephen Hillenburg for Nickelodeon.
 "SpongeBob SquarePants" chronicles the adventures and endeavors of the title character and his various friends in the fictional underwater city of Bikini Bottom.
 Many of the ideas for the show originated in an unpublished, educational comic book titled "The Intertidal Zone", which Hillenburg created in the mid-1980s.
 He began developing "SpongeBob SquarePants" into a television series in 1996 upon the cancellation of "Rocko's Modern Life", which Hillenburg directed.
 The pilot episode first aired on Nickelodeon in the United States on May 1, 1999.
 The show's ninth season premiered in 2012, and episodes of "SpongeBob SquarePants" have aired.
 A feature-length film adaptation of the show, "The SpongeBob SquarePants Movie", was released in 2004; in 2015, a sequel, "", was released.
Help Wanted (SpongeBob SquarePants)
"Help Wanted" is the pilot episode of the American animated television series "SpongeBob SquarePants".
 It originally aired on Nickelodeon in the United States on May 1, 1999, following the television airing of the 1999 Kids' Choice Awards.
 The episode follows the protagonist, an anthropomorphic sea sponge named SpongeBob SquarePants, attempting to get a job at a local restaurant called the Krusty Krab.
 However, he is tasked to find a seemingly non-existent high-caliber spatula because the owner, Mr. Krabs, considers him unqualified for the position.
 Eventually, crowds of ravenous anchovies stop by the Krusty Krab and demand meals.
 SpongeBob returns from his errand, having fulfilled the request of Mr. Krabs and found a mechanical spatula.
 He utilizes the spatula to fulfill the anchovies' hunger.
 SpongeBob is then welcomed by Mr. Krabs as a Krusty Krab employee.
SpongeBob SquarePants 4D: The Great Jelly Rescue
SpongeBob SquarePants 4D: The Great Jelly Rescue (often referred to as SpongeBob SquarePants 4D or simply The Great Jelly Rescue) is a 4-D film attraction that serves a sequel to SpongeBob SquarePants 4-D.
 It follows SpongeBob, Patrick, and Sandy as they go jellyfishing.
The SpongeBob SquarePants Movie
The SpongeBob SquarePants Movie is a 2004 American live-action/animated comedy film based on the Nickelodeon television series "SpongeBob SquarePants".
 The film was co-written, directed, and co-produced by series creator Stephen Hillenburg and starred the series' cast of Tom Kenny, Bill Fagerbakke, Clancy Brown, Rodger Bumpass and Mr. Lawrence, with guest performances by Scarlett Johansson, Jeffrey Tambor, Alec Baldwin and David Hasselhoff.
 It was produced by Hillenburg's production company United Plankton Pictures and Nickelodeon Movies, it was distributed by Paramount Pictures and was also the first film in the "SpongeBob SquarePants" film series.
 In the film, Plankton devises a plan to steal King Neptune's crown and send it to Shell City, and SpongeBob and Patrick must retrieve the crown to save Mr. Krabs from King Neptune's wrath and Bikini Bottom from Plankton's plan.
The SpongeBob Movie: Sponge Out of Water
The SpongeBob Movie: Sponge Out of Water is a 2015 American 3D live-action/animated comedy film based on the animated television series "SpongeBob SquarePants".
 A stand-alone sequel to "The SpongeBob SquarePants Movie" (2004), it was directed by former series showrunner Paul Tibbitt in his directorial debut, with live-action sequences directed by Mike Mitchell.
 It was the first film to be produced by Paramount Animation and second film in the "SpongeBob SquarePants" film series.
 The film stars Antonio Banderas and features the show's regular voice cast, who returned to reprise their respective roles from the series and the previous film.
 The plot follows a pirate called Burger-Beard, who steals the Krabby Patty secret formula using a magical book that makes any text written upon it come true.
 SpongeBob and his friends must travel to the surface to confront Burger-Beard and get the formula back.
SpongeBob SquarePants: Lights, Camera, Pants!
SpongeBob SquarePants: Lights, Camera, Pants!
 is a 2005 party video game based on the TV series "SpongeBob SquarePants".
 It was released in October 2005 for the Xbox, PlayStation 2, GameCube, Game Boy Advance, and the PC.
 It was released for the Nintendo DS in Korea in 2007, but its North American release was cancelled.
 It is the first "SpongeBob SquarePants" title to feature multiplayer mini-games, similar to the "Mario Party" video game series.
 It is also the last SpongeBob game for the Xbox.
 It is also the last time Charles Nelson Reilly would voice the Dirty Bubble before his death in 2007.
 For reasons unknown, Mermaid Man was not voiced by his original voice actor Ernest Borgnine but instead Joe Alaskey, who would voice him again in .

Question: In which year, did this earliest guest star in 1999 for SpongeBob SquarePants stop providing the voice?
Answer: 2012