"I Want a Pony" is one of those unrealistic things that kids will ask for. Children lack understanding of the cost of owning a pony in time, labor, and money. Even when such things are explained, the child wants a pony anyway.
This is a metaphor for customers who ask for products that are small, fast, reliable, cheap, first to market, and fully-featured. Even when the costs and other tradeoffs are explained to them they still want the durn pony.
In a meeting this idomatic phrase can be a striking reminder that a group is building a fantasy wish list:
Bonus reply: "Um, that was no lamp."
Discussion:
I have looked at some of the projects described on RentACoder http://www.rentacoder.com. They want a full-featured clone of Amazon.com or some dating site and they want it for $200 US. The expectation is so unrealistic as to be simply fantasy. -- MartinChernenkoff
It is more likely a troll or just a joke. Nobody in their right mind could ask for such a thing, so one has to assume the absurdity is intentional.
In the UK, "pony" is slang for �25, so when your child asks for a pony, you simply hand over the dosh.
Another phrase with identical concept is I want the moon on a stick.
One is reminded of http://www.stlyrics.com/lyrics/willywonkaandthechocolatefactory/iwantitnowoompaloompa.htm
[Note that this song is sung (in great part) by the character Veruca Salt, not to be confused with the Chicago-based band. (http://www.verucasalt.com)]
I think the agile idea is to not let the customer ask for the pony. Or rather, they can ask for it and everything else, but then they must spend the "cash" (available programmer time) to "buy" only the things they really need. It will be clear to them that the cost of the metaphorical pony will far outstrip the "cash" they have to spend.
Let's please not get too deep here. Analogy is a wonderful thing in moderation. Be moderate.
{Damn, now I have to shelf my "pony droppings" analogy.}
[Yes, we don't want to be "sweeping up" after you and your analogy, sir! <cough>]
A good line for this situation from NASCAR guys, the old hillbilly magician types; "Fast, reliable, cheap. Pick two."
Similar examples are found under IncompatibleGoals.
See: KillerUserInterface, PersonalChoiceElevatedToMoralImperative