Elwood Blues, was partly based on Felix the Cat, the black and white, and Felix's "Magic Bag of Tricks" became Elwood's briefcase handcuffed to his wrist, that he carried onstage to retrieve his harmonica from

According to Aykroyd he based the black and white look of the brothers and the bag that Elwood carries around, on the popular comic strip and cartoon character.

For those interested, Aykroyd makes his Felix reference around the 14:05 mark in this episode of the Fly on the Wall podcast  https://open.spotify.com/episode/6gxrIjHrQUyTnX6Sl95JyT

https://www.theguardian.com/film/2020/aug/03/how-we-made-the-blues-brothers-dan-aykroyd-john-landis-interview

https://www.facebook.com/groups/dougwrightawards/posts/10161832465062164