That’s a horse of a different story

This is a blend of “a horse of a different color” (an entirely different matter) and “that’s another (or different) story” (an explanation to give at some other time).   A big thanks to Robyn Pietrucha who heard this malaphor spoken in the 1934 comedy short, “The Chases of Pimple Street”, starring Charley Chase.   The movie is a spoof of the 1934 classic, “The Barretts of Wimpole Street”.

http://en.wikipedia.org/wiki/Charley_Chase