Question: Writer Romeo Muller and actor Jackie Vernon worked in a 1976 animated Christmas television special which is owned by who? 

Context paragraphs:
Frosty the Snowman (film): Frosty the Snowman is a 1969 animated Christmas television special based on the song "Frosty the Snowman".  The program, which first aired on December 7, 1969 on CBS (where it still airs to this day), was produced for television by Rankin/Bass Productions and featured the voices of comedians Jimmy Durante as the film's narrator (Durante's final performance in a film) and Jackie Vernon as the title character.

A Flintstone Family Christmas: A Flintstone Family Christmas is a 1993 animated Christmas television special featuring The Flintstones.  It was produced by Hanna-Barbera and aired on ABC on December 18, 1993.  The special was nominated for a Primetime Emmy Award in 1994 for Outstanding Animated Program (For Programming Less Than One Hour).  This is the only appearance of Stoney and the final appearance of Pebbles and Bamm-Bamm in their adult forms as well as their children, Chip and Roxy.  Hanna-Barbera continued doing the series but with the original timeline.

Jack Frost (1979 film): Jack Frost is a 1979 Christmas stop motion animated television special produced by Rankin/Bass Productions.  It was directed by Jules Bass and Arthur Rankin, Jr., written by Romeo Muller and premiered on the NBC network on December 13, 1979.  The special tells the tale of Jack Frost, the winter sprite, and his adventures as a human.

Rankin/Bass Productions: Rankin/Bass Productions, Inc. (founded as Videocraft International, Ltd.) was an American production company, known for its seasonal television specials, particularly its work in stop motion animation.  The pre-1974 library is owned by Universal Studios (via DreamWorks Animation/DreamWorks Classics), while the post-1973 library is owned by Warner Bros. Rankin/Bass stop-motion features are recognisable by their visual style of doll-like characters with spheroid body parts, and ubiquitous powdery snow using an animation technique called "Animagic".  Often, traditional cel animation scenes of falling snow would be projected over the action to create the effect of a snowfall.

Yogi Bear's All Star Comedy Christmas Caper: Yogi Bear's All Star Comedy Christmas Caper is a 1982 animated Christmas television special starring Yogi Bear.  It is the third and final Yogi Christmas special.  Produced by Hanna-Barbera, it first aired on  21, 1982 (1982--) on CBS.

The World of Strawberry Shortcake: The World of Strawberry Shortcake is a 1980 animated television special written by Romeo Muller, directed by Charles Swenson, and produced by Swenson, Muller and Fred Wolf.  Starring the voices of Romeo Muller, Russi Taylor, Julie McWhirter and Joan Gerber, it was made by animators from Murakami-Wolf-Swenson in the United States and by Toei Doga in Japan.  The music was written and performed by Flo & Eddie of the rock group, The Turtles.

A Flintstone Christmas: A Flintstone Christmas is a 1977 animated Christmas television special featuring characters from "The Flintstones" franchise.  It was produced by Hanna-Barbera and is the second Christmas-themed animated work in the franchise, after the 1964 episode "Christmas Flintstone."  Both feature the character Fred Flintstone taking on the role of Santa Claus.

Strawberry Shortcake in Big Apple City: Strawberry Shortcake in Big Apple City is a 1981 animated television special written by Romeo Muller, produced by Muller and Buzz Potamkin, and directed by Hal Silvermintz.  This is the second special to feature the American Greetings character, Strawberry Shortcake.

Frosty's Winter Wonderland: Frosty's Winter Wonderland is a 1976 animated Christmas television special and a sequel to the 1969 special "Frosty the Snowman", produced by Rankin/Bass Productions.  It returns writer Romeo Muller and actor Jackie Vernon as the voice of Frosty, while Andy Griffith stars as the narrator.  The special premiered on ABC on December 2, 1976.

The Little Troll Prince: The Little Troll Prince (onscreen title: The Little Troll Prince: A Christmas Parable) is a 1987 animated Christmas television special produced by Hanna-Barbera.  Backed by the International Lutheran Laymen's League, it has strong Christian themes of unconditional love, self-sacrifice, and redemption, with a substantial Protestant influence.  The story was a written parable script for the Christmas special with a lesson about the feeling of joy and love in one's heart, that can lead one from a cruel world to a light-hearted world.

Supporting paragraphs: Frosty's Winter Wonderland Rankin/Bass Productions
Answer: by Warner Bros.