Saying that phrase isn't necessary...

[2gigch1]

I usually go with 'no thanks, we'll save a plastic tree today.'

A very few times I have had people take me seriously, and try to explain to me there is no such thing as a plastic tree. Those are usually the harbingers of weird days.

[Pojodan]

What got me, back when I worked as a bag boy at a grocery store, was the people that wanted paperbags INSIDE plastic bags.

These ones ALWAYS were completely obsessive about what items went where

"No, no, no, the rice bag goes ONTOP of the oatmeal"
"No, stop, the soup cans go on their side on the BOTTOM, and the vegitable cans sit on their top over the soup cans, but no more than 5 each per bag"

UGH!

One regular, which I learned to avoid if I could, had a convoluted process that involved bags inside of bags, specific numbers of bags inside of bags, inside of bags, and the thing that stuck out the most was that the eggs went ONTOP of the bread.

I can't say I blame people, as some of my coworkers were utterly wreckless, so much that the General manager pulled all of us aside at one point and showed us a lady's bags that had just been bagged, in which every item that was in any way delicate (eggs, bread, tomatoes, etc) were at the BOTTOM of bags with cans and boxes piled ontop. Quite infuriating.

[dragon_wings]

I usually go with 'no thanks, we'll save a plastic tree today.'

A very few times I have had people take me seriously, and try to explain to me there is no such thing as a plastic tree. Those are usually the harbingers of weird days.

QFT.
I say this on occasion (as the cashier) and get some odd looks. Then there are the people that get it and play along. But then I'll take any chance to be sarcastic and get away with it.

[dalesys]

we'll save a plastic tree today.

Down in robot city you might think it's play, play, play
But a number 5 robot he must work in all the night and day

Number 1 come by, he give my work to me
Oil the flowers, fix the showers, clean the electronic trees

--- Robot Blues, The Incredible String Band

[EricKei]

What got me, back when I worked as a bag boy at a grocery store, was the people that wanted paperbags INSIDE plastic bags.

While the reverse is often seen here (because things like milk "sweat" heavily in humid climates like mine, I have seen people who want paper-in-plastic. Mainly it's so they can have an ersatz handle to make them a bit easier to carry, while (theoretically) still having the strength and capacity of a paper bag.

[noone]

I usually reply "no thank you!"

Occasionally I call out customers, which vents their SC rage on me instead of the cashier. I take one for the CS team.

[Yarnil]

Here in the Netherlands, if you ant a bag, you have to pay 10ct for it. (Or take a very thin plastic bag you can also put the greens in)

No baggers either here