He wrote and directed many animated cartoon shorts starring Bugs Bunny, Daffy Duck, Porky Pig, Foghorn Leghorn, Hippety Hopper, Speedy Gonzales, and the Tasmanian Devil, among other characters.

[3] In mid-1929, Robert was offered a job at Walt Disney Studio as an assistant animator to Dick Lundy, while Tom apprenticed under Norm Ferguson.

[8] He accepted his own directorial position in late 1944, when Frank Tashlin left Warner Bros. to direct live-action films.

McKimson created characters like Foghorn Leghorn and the Tasmanian Devil, as well as directing every Hippety Hopper/Sylvester pairing.

He also created Speedy Gonzales for the 1953 short Cat-Tails for Two and directed many others periodically (along with Friz Freleng and other directors) for the remainder of his theatrical career.

[12] Soon, McKimson assembled a new team of artists, including layout man/background painter Robert Gribbroek (formerly of Jones's unit) plus animators Warren Batchelder, Ted Bonnicksen, George Grandpré and Tom Ray.

[13] McKimson continued working at Warner's Cartoon Studio as it began to lose staff (including such key personnel as Jones) in the early 1960s.

According to an interview with his son, he generally did not like how things were going at the studio and missed full animation, as well as disliking the new characters in the new shorts.

[13] Over this time, he directed his share of shorts and worked on the feature The Incredible Mr. Limpet with Hawley Pratt, taking over the role of director from Bill Tytla due to his illness.

McKimson was the one person to be at the studio from the start of the Looney Tunes series through its finish in 1969, first as an animator and then as a director.

At the time of his death, he had recently completed directing Misterjaw and had begun work on Baggy Pants and the Nitwits.

[8] In addition to being an animator, McKimson was a skilled horseman and polo player, a dedicated bowler, and a Master Mason.