Horse of a different color

I recently heard someone use the expression "Now that's a whole different bag of dog food". While highly unusualy, the meaning was well understood by the audience. I know there is an actual idiom/expression used more normally than this one, but I cannot recall what it is.

"Horse of a different color" comes to mind, but I don't think that's it. Is there another equivalent expression in common use? I'd prefer one centered around the words "whole different/whole new", since I believe this expression was a play one such a phrase.

Solution 1:

That's a whole different kettle of fish.

Solution 2:

I don't think "whole other can or worms" or its variants is really synonymous. "Horse of a different color" means "categorically different", "can of worms" contains the meaning of "unleashing a large number of unanticipated problems.".

A synonymous phrases would be "cut from a different cloth", or "apples and oranges", though you'd have to shape them appropriately to you specific needs. If you need to go folksy, you could try "thems be apples and oranges, so they be."

As far as dog food? Google doesn't know what you are talking about: http://books.google.com/ngrams/graph?content=whole+different+bag+of+dog+food%2C+horse+of+a+different+color&year_start=1800&year_end=2000&corpus=0&smoothing=3

Solution 3:

I've figured it out. The expression I was looking for was "a whole new ball game".

I wonder - is this a uniquely American expression?