This'll Make You Whistle is a 1936 British musical comedy film directed by Herbert Wilcox and starring Jack Buchanan, Elsie Randolph and William Kendall.
 The film was based on a stage play which Buchanan had starred in.
When Knights Were Bold is a 1936 British musical comedy film directed by Jack Raymond and starring Jack Buchanan, Fay Wray and Garry Marsh.
 Songs include "Let's Put the People To Work" sung by Jack Buchanan, "Onward We Go" sung by Buchanan & soldiers' chorus, and "I'm Still Dreaming" sung by Buchanan.
Fred Astaire (born Frederick Austerlitz; May 10, 1899 – June 22, 1987) was an American dancer, singer, actor, choreographer and television presenter.
Nanette Fabray (born October 27, 1920) is an American actress, dancer and singer.
 She began her career performing in vaudeville as a child and became a musical theatre actress during the 1940s and 1950s, winning a Tony Award in 1949 for her performance in "Love Life".
 In the mid-1950s, she served as Sid Caesar's comedic partner on "Caesar's Hour", for which she won three Emmy Awards, as well as co-starring with Fred Astaire in the film musical "The Band Wagon".
 From 1979 to 1984, she appeared as Grandma Katherine Romano on the TV series "One Day at a Time".
Walter John "Jack" Buchanan (2 April 1891– 20 October 1957) was a Scottish theatre and film actor, singer, dancer, producer and director.
 He was known for three decades as the embodiment of the debonair man-about-town in the tradition of George Grossmith Jr., and was described by "The Times" as "the last of the knuts."
 He is best known in America for his role in the classic Hollywood musical "The Band Wagon" in 1953.
"That's Entertainment!"
 is a popular song with music written by Arthur Schwartz and lyrics by Howard Dietz.
 The song was published in 1952 and was written especially for the 1953 Metro-Goldwyn-Mayer musical film "The Band Wagon".
 The song is performed in the film by Jack Buchanan supported by Fred Astaire, Nanette Fabray, and Oscar Levant.
 In 2004 the song finished at #45 in AFI's 100 Years...100 Songs survey of top tunes in American cinema.
Break the News is a 1938 British musical comedy film directed by René Clair and starring Jack Buchanan, Maurice Chevalier and June Knight.
 Two struggling performers decide to create a fake murder scandal in order to drum up publicity for their act.
 It was based on the novel "Le mort en fuite" by Loïc Le Gouriadec which had previously been made into a 1936 French film "Death on the Run".
 Songs featured include "It All Belongs to You" (Cole Porter, sung by Chevalier) and "We're Old Buddies" (Van Phillips, Jack Buchanan, sung by Chevalier and Buchanan).
The Sky's the Limit is a 1938 British musical comedy film directed by Jack Buchanan and Lee Garmes and starring Buchanan, Mara Losseff and William Kendall.
Come Out of the Pantry is a 1935 British musical film directed by Jack Raymond and starring Jack Buchanan, Fay Wray, James Carew and Fred Emney.
Goodnight, Vienna (also known as Magic Night) is a 1932 British musical film directed by Herbert Wilcox and starring Jack Buchanan, Anna Neagle and Gina Malo.
 Two lovers in Vienna are separated by the First World War, but are later reunited.

Question: Which American dancer, singer, actor, choreographer and television presenter supported Jack Buchanan when he performed That's Entertainment! in the musical film The Band Wagon?
Answer: Fred Astaire