"Charley's Aunt" is a classic and well-loved play. Jack Benny starred in a movie version of the play, and that movie is well worth seeing. This movie, however, is not a film version of the play.
"Charley's Big-Hearted Aunt" is a clever and very funny take-off of the play. Arthur Askey is very funny as Lord Fancourt Babberly, who is starring in the play "Charley's Aunt" while attending Oxford. He is reluctantly talked into playing the part of his classmate's wealthy aunt (since he already has experience at playing an aunt) to avoid getting kicked-out of school. The real aunt, of course, shows-up. The writing cleverly weaves elements of the actual play in and out of the story.
I managed to get a nice copy of this on EBAY for $4.00.