June 4, 1944 – The last episode sponsored by Grape Nuts Flakes. Dennis Day is gone to Naval training and Phil Harris sings “G.I. Jive”.
Plus songs “A Slip of the Lip Can Sink a Ship”, “Oh, What a Beautiful Morning”, and Swing and Sway with Sammy Kaye.
They mention a number of radio comedies and the soap opera John’s Other Wife. And the actor C. Aubrey Smith.
Jack Benny Episodes 
If I recall properly, Phil also sings “G.I. Jive” on the next episode, the Season Opener where Jack visits his sponsor who had earlier spoke with Fred Allen. Unless I’m mixing up season premieres?