July 4, 1942 - Army private "Slim" Samson is released from the brig to find a mysterious package waiting for him in the barracks. Turns out "Slim" has inherited the effects of his recently deceased, cartoonist uncle, Sam. Included in the effects are a fancy old pen and the design of Uncle Sam's last creation, a patriotic superhero called Yankee Doodle. "Slim" and his pal Danny O'Hara think the character silly until "Slim" opens his uncle's fancy old pen and finds himself transformed into YANKEE DOODLE! He's invulnerable to harm, super-strong, and...flat as a piece of paper. Now, with the ability to slip under (or break through) any door and bounce bullets "Slim" thwarts Nazi and Japanese saboteurs as AMERICA'S ODDEST DEFENDER... assuming Danny can keep the suspicious Sergeant Parris off his back.