The Seven little Foys
"High point is a Friar's testimonial dinner to Foy in which James Cagney as George M.Cohan,exchanges kidding  insult-on-the square with hope, then both swing into a lovely, graceful soft-shoe challenge routine to the tune of Cohan's "Mary." the sequence captures all the hard-shelled sentimentality of the old pros,emerging as a warming tribute to Foy and Cohan from two latter-day pros,Hope and Cagney"

                               Saturday Review
                        Film Facts

Cagney played  a cameo bit as George M. Cohan , he lost 15 pounds and rehearsed for three weeks with Hope.Both carney's knees swelled during the rehearsal, but always the tough guy filmed the scene without  saying a word. Once the scene was shot he called Hope into his dressing room ,both were shocked to see his knees filled with fluid. easily twice their size,they were back to normal within a week. 
1955