Question: Mister Magoo stars an actor who provided the voice of what character on "The Rocky and Bullwinkle Show"?
Context: The Adventures of Rocky and Bullwinkle is a 2000 live action/animated adventure comedy film produced by Universal Pictures, based on the television cartoon "The Rocky and Bullwinkle Show" by Jay Ward.  The animated characters Rocky and Bullwinkle shared the screen with live actors portraying Fearless Leader (Robert De Niro), Boris Badenov (Jason Alexander), Natasha Fatale (Rene Russo), Piper Perabo, Randy Quaid, Kenan Thompson, and Kel Mitchell.  Reprising her role as Rocky was June Foray, and Keith Scott voices Bullwinkle and the film's narrator. Rocket J. "Rocky" Squirrel is a plucky flying squirrel and one of the two protagonists of the 1959–1964 animated television series "Rocky and His Friends" and "The Bullwinkle Show" (both shows often referred to collectively as "The Rocky and Bullwinkle Show"), produced by Jay Ward.  Rocky is the best friend and ally of the western moose, Bullwinkle.  Both Rocky and Bullwinkle were given the middle initial "J" as a reference to Ward. Captain Peter “Wrongway” Peachfuzz was a supporting character on the animated television programs "Rocky and His Friends" and "The Bullwinkle Show", now known collectively as "The Rocky and Bullwinkle Show".  He made his debut in "Jet Fuel Formula", the first Rocky & Bullwinkle story arc, originally broadcast late 1959 and early 1960. Rocky & Bullwinkle is a 2014 American computer-animated direct-to-video short film based on the 1960s animated television series "The Rocky and Bullwinkle Show".  It was produced by DreamWorks Animation and distributed by 20th Century Fox.  Gary Trousdale, best known for co-directing Disney's "Beauty and the Beast", served as the director, while Robert Ben Garant and Thomas Lennon were the writers (They also provided the voices of Fearless Leader and the narrator for this short).  June Foray reprises her role as Rocky, in her final reprisal of the role before her passing on July 27, 2017 (as well as her final role overall), while Tom Kenny voices Bullwinkle.  It was released on October 14, 2014 on the Blu-ray 3D of "Mr. Peabody and Sherman" (which is also based on characters from "The Rocky & Bullwinkle Show"). Gidney and Cloyd are fictional characters originally appearing in the American animated television program "Rocky and His Friends" (now known, along with "The Bullwinkle Show", as "The Rocky and Bullwinkle Show" or simply "Rocky and Bullwinkle").  Their names were adapted from the names "Sidney" and "Floyd", which Jay Ward said were the most boring names ever.  (Gidney is also an actual surname indigenous to New England and neighboring areas of Canada.  Cloyd is both an actual surname and a given name—see former major league baseball player Cloyd Boyer as well as current major league baseball player Tyler Cloyd.) Natasha Fatale is an antagonist of the 1959–1964 animated cartoons "Rocky and His Friends" and "The Bullwinkle Show", collectively referred to as "The Rocky and Bullwinkle Show".  She was voiced by June Foray. Bullwinkle J. Moose is a fictional character in the 1959–1964 animated television series "Rocky and His Friends" and "The Bullwinkle Show", often collectively referred to as "Rocky and Bullwinkle", produced by Jay Ward and Bill Scott.  When the show changed networks from ABC to NBC, its name was changed to "The Bullwinkle Show", reflecting the popularity of Bullwinkle. Solomon Hersh Frees (June 22, 1920 – November 2, 1986), better known as Paul Frees, was an American actor, voice actor, impressionist, comedian and screenwriter known for his work on MGM, Walter Lantz, and Walt Disney theatrical cartoons during the Golden Age of Animation and for providing the voice of Boris Badenov in "The Rocky and Bullwinkle Show".  As with contemporary, Mel Blanc, he became known as "The Man of a Thousand Voices." Mister Magoo is an American animated television series which was produced from November 7, 1960, to February 2, 1962.  A single episode included five 4 minute shorts and could either be aired together with bumpers as a single half-hour show, or it could be split up with one short aired each weekday, along with other cartoons.  It was produced by United Productions of America.  The series stars Jim Backus, Mel Blanc, Jerry Hausner, Paul Frees and Frank Nelson. Fearless Leader is a fictional character and a recurring antagonist in the 1959–1964 animated television series "Rocky and His Friends" and "The Bullwinkle Show", both shows often collectively referred to as "The Rocky and Bullwinkle Show".  He was voiced by Bill Scott.
Answer: Boris Badenov