[kvanbrunt2]

and it looks stupid. but the current flag is kinda weird too. i’ve been to the island and i have no idea what the four stars represent. the country is basically two big islands with a lot of smaller ones. i have a Waiheke island passport.
at wiki: The Realm of New Zealand also includes Tokelau (a dependent territory); the Cook Islands and Niue (self-governing states in free association with New Zealand); i guess those are the four stars.

[goldstategop]

Four stars allegorically represent the Southern Cross.

Australia has a somewhat different arrangement.

[naturalman1975]

The four stars are a representation of Crux - the Southern Cross - one of the most prominent constellations in the Southern sky that can be seen all year around. Australia has a similar flag (although ours have the five brightest stars of the constellation rather than the four brightest). This debate about changing the flag comes up in Australia periodically - normally from the left - and while what New Zealand does is a matter for New Zealand, there's a pro-flag poem in Australia that is also largely true of New Zealand as well (though not totally):

Our flag bears the stars that shine at night
In our southern sky of blue
And there's a little old flag in the corner
That is part of our heritage too,

It's the English, the Scots and the Irish
Who were sent to the end of the earth
The rogues and the schemers, the doers and dreamers
Who gave modern Australia birth.

And you who are shouting to change it
You don't seem to understand
It's the flag of our laws and language
Not the flag of some far away land

Though, there's plenty who'll tell if you ask them
How when Europe was plunged into night
How that little old flag in the corner
Was a symbol of freedom and light.

It doesn't mean we owe our allegiance
To some forgotten imperial dream
We've got the stars to show where we're going
And the old flag to show where we've been

It's only an old piece of bunting
It's only an old coloured rag
But there's thousands who died for its honour
And fell in defence of our flag.

[reed13k]

Four stars represent the constellation of the Southern Cross (similar to the southern hemisphere as Polaris the north star is to the northern hemisphere).

The fact that it is indeed representative of the cross likely also has some impact.