Question: Who co-founded the developer of Intellivision?

full_context: Document 1: Elliot Handler: Elliot Handler (April 9, 1916 – July 21, 2011) was an American inventor, businessman, and co-founder of Mattel. With his wife, he developed some of the biggest-selling toys in American history, including Barbie, Chatty Cathy, Creepy Crawlers, and Hot Wheels.
Document 2: Toys "R" Us: Founded by Charles Lazarus in its modern incarnation in 1957, Toys ``R ''Us traced its origins to Lazarus's children's furniture store, which he started in 1948. He added toys to his offering, and eventually shifted his focus. The company had been in the toy business for more than 65 years and operated around 800 stores in the United States and around 800 outside the US, although these numbers have steadily decreased with time.
Document 3: TRS-80: The TRS-80 Micro Computer System (TRS-80, later renamed the Model I to distinguish it from successors) is a desktop microcomputer launched in 1977 and sold by Tandy Corporation through their RadioShack stores. The name is an abbreviation of "Tandy/RadioShack, Z80 microprocessor". It is one of the earliest mass-produced and mass-marketed retail home computers.
Document 4: History of video games: The Magnavox Odyssey never caught on with the public, due largely to the limited functionality of its primitive technology. By the middle of the 1970s, however, the ball - and - paddle craze in the arcade had ignited public interest in video games and continuing advances in integrated circuits had resulted in large - scale integration (LSI) microchips cheap enough to be incorporated into a consumer product. In 1975, Magnavox reduced the part count of the Odyssey using a three - chip set created by Texas Instruments and released two new systems that only played ball - and - paddle games, the Odyssey 100 and Odyssey 200. Atari, meanwhile, entered the consumer market that same year with the single - chip Home Pong system designed by Harold Lee. The next year, General Instrument released a ``Pong - on - a-chip ''LSI and made it available at a low price to any interested company. Toy company Coleco Industries used this chip to create the million - selling Telstar console model series (1976 -- 77), while dozens of other companies released models as well. Overall, sales of dedicated ball - and - paddle systems in the U.S. grew from 350,000 in 1975 to a peak of 5 -- 6 million in 1977. A similar boom hit the United Kingdom and other parts of Europe, with much of the market supplied by clone manufacturers in Hong Kong.
Document 5: Beanie Babies: Nine original Beanie Babies were launched in 1993: Legs the Frog, Squealer the Pig, Spot the Dog, Flash the Orca, Splash the Whale, Chocolate the Moose, Patti the Platypus, Brownie the Bear (later renamed ``Cubbie ''), and Pinchers the Lobster (with some tag errors with`` Punchers''). They were not in factory production until 1994. Sales were slow at first to the point that by 1995 many retailers refused to buy the products in the bundles Ty offered them while others outright refused to buy them in any form. The popularity soon grew however, first starting locally in Chicago before growing into a national craze in the USA.
Document 6: Teddy Ruxpin: From his debut in September 1985 various toy makers have produced Teddy Ruxpin over the years. The first was Worlds Of Wonder from 1985 until its bankruptcy in 1988. The toy's rights were then sold to Hasbro, and produced again from 1991 to 1996. Another version debuted in 1998 by YES! Entertainment with another version in 2006, produced by BackPack Toys. Presently Teddy Ruxpin is available from Wicked Cool Toys.
Document 7: Intellivision: The Intellivision is a home video game console released by Mattel Electronics in 1979. The name "Intellivision" is a portmanteau of "intelligent television". Development of the console began in 1977, the same year as the introduction of its main competitor, the Atari 2600. In 1984 Mattel sold their video game assets to a former Mattel Electronics executive and investors that would become INTV Corporation. Games development started in 1978 and continued until 1990 when the Intellivision was discontinued. From 1980 to 1983 over 3 million Intellivision units were sold.
Document 8: Cabbage Patch Kids: Cabbage Patch Kids Type Dolls Company Coleco (1982 -- 1988) Hasbro (1988 -- 1994) Mattel (1994 -- 2003) Toys ``R ''Us (2003) Play Along (2004 -- 2011) Jakks Pacific (2011 -- 2014) Wicked Cool Toys (2015 -- present) Country United States Availability 1978 -- present Official website
Document 9: Beanie Babies: Nine original Beanie Babies were launched in 1993: Legs the Frog, Squealer the Pig, Spot the Dog, Flash the Orca, Splash the Whale, Chocolate the Moose, Patti the Platypus, Brownie the Bear (later renamed ``Cubbie ''), and Pinchers the Lobster (with some tag errors with`` Punchers''). They were not in factory production until 1994. Sales were slow at first to the point that by 1995 many retailers refused to buy the products in the bundles Ty offered them while others outright refused to buy them in any form. Their popularity soon grew however, first starting locally in Chicago before growing into a national craze in the USA.
Document 10: Sea Battle: Sea Battle is a multiplayer strategy game released by Mattel for its Intellivision video game system in 1980. In the game, players command fleets of naval vessels attempting to invade the harbor of their opponent.
Document 11: Nintendo: Nintendo's first venture into the video gaming industry was securing rights to distribute the Magnavox Odyssey video game console in Japan in 1974. Nintendo began to produce its own hardware in 1977, with the Color TV - Game home video game consoles. Four versions of these consoles were produced, each including variations of a single game (for example, Color TV Game 6 featured six versions of Light Tennis).
Document 12: Video game console: The first video games appeared in the 1960s. They were played on massive computers connected to vector displays, not analog televisions. Ralph H. Baer conceived the idea of a home video game in 1951. In the late 1960s, while working for Sanders Associates, Baer created a series of video game console designs. One of these designs, which gained the nickname of the 1966 ``Brown Box '', featured changeable game modes and was demonstrated to several TV manufacturers, ultimately leading to an agreement between Sanders Associates and Magnavox. In 1972, Magnavox released the Magnavox Odyssey, the first home video game console which could be connected to a TV set. Ralph Baer's initial design had called for a huge row of switches that would allow players to turn on and off certain components of the console (the Odyssey lacked a CPU) to create slightly different games like tennis, volleyball, hockey, and chase. Magnavox replaced the switch design with separate cartridges for each game. Although Baer had sketched up ideas for cartridges that could include new components for new games, the carts released by Magnavox all served the same function as the switches and allowed players to choose from the Odyssey's built - in games.
Document 13: Nintendo Entertainment System: The Nintendo Entertainment System (commonly abbreviated as NES) is an 8 - bit home video game console that was developed and manufactured by Nintendo. It was initially released in Japan as the Family Computer (Japanese: ファミリーコンピュータ, Hepburn: Famirī Konpyūta) (also known by the portmanteau abbreviation Famicom (ファミコン, Famikon) and abbreviated as FC) on July 15, 1983, and was later released in North America during 1985, in Europe during 1986 and 1987, and Australia in 1987. In South Korea, it was known as the Hyundai Comboy (현대컴보이 Hyeondae Keomboi) and was distributed by SK Hynix which then was known as Hyundai Electronics. The best - selling gaming console of its time, the NES helped revitalize the US video game industry following the video game crash of 1983. With the NES, Nintendo introduced a now - standard business model of licensing third - party developers, authorizing them to produce and distribute titles for Nintendo's platform. It was succeeded by the Super Nintendo Entertainment System.
Document 14: National Toy Hall of Fame: The National Toy Hall of Fame is an American hall of fame that recognizes the contributions of toys and games that have sustained their popularity for many years. Criteria for induction include: icon status (the toy is widely recognized, respected, and remembered); longevity (more than a passing fad); discovery (fosters learning, creativity, or discovery); and innovation (profoundly changed play or toy design). Established in 1998 under the direction of Ed Sobey, it was originally housed at A.C. Gilbert's Discovery Village in Salem, Oregon, United States, but was moved to the Strong National Museum of Play (now The Strong) in Rochester, New York, in 2002 after it outgrew its original home.
Document 15: Adventures of Tron: Adventures of Tron is an action game produced by Mattel in 1982 and the Atari 2600 version of the Intellivision video game "". It is based on the Disney film "Tron".
ground_truth: Elliot Handler
sub_queries: What company built Intellivision? Answer: Mattel
Mattel >> founded by Answer: Elliot Handler