Eating a frog seems to be a metaphor for getting unpleasant tasks out of the way.

"that" is just the usual determiner; "that frog" has a nuance of "the (metaphorical) frog that you know about from the old saying", as explained at http://home.earthlink.net/~denmartin/etf.html

soheil1What does 'that' mean

that frog = the frog which is there
that house = the house which is there
that letter = the letter which is there

And so on.

In the case of the title, it's whichever frog is there in front of you.

CJ

CalifJimIn the case of the title, it's whichever frog is there in front of you.

I'm fairly sure it doesn't mean that.

Demonstrative adjective :-)

Michael Rushworth Demonstrative adjective :-)

I know "adjective" is the traditional label, but personally I have a lot of difficulty with that. Many dictionaries now refer to it as a "determiner". On the other hand, I seem to remember reading that not everyone likes that either.

Yes. Demonstrative Adjective as a sub category of deteminer.

Too much relies on personal preference, I suppose.

GPY CalifJimIn the case of the title, it's whichever frog is there in front of you.I'm fairly sure it doesn't mean that.

How do you figure? Given that "frog" is metaphoric for "major task" or "high priority task", as explained in the given link, which other "frog" (or "task") can "that frog" / "that task" be except the one there, befor