Trick or Treat? Or Tricks or Treats?

Is it "trick or treat" or "tricks or treats"? Singular or plural?

Every time I watch “It’s the Great Pumpkin, Charlie Brown,” I'm reminded of a linguistic question I've had since childhood.

The story is simple. Young Linus convinces Sally to wait with him in a local pumpkin patch, expecting the Great Pumpkin to arrive with toys for all the good children. In the meantime, the other kids go trick-or-treating, getting candy (or rocks) from their neighbors.

In my neighborhood, we said we were "going out for trick or treat." Or we turned the phrase into a verb and said "Let's go trick-or-treating." At the door, we always said "trick or treat."

In Charlie Brown's neighborhood, there's a mix. Lucy says "tricks or treats" when she's explaining the process to Sally. But at one house, she uses the singular: "trick of treat."

Later, when (spoiler alert!) Snoopy the dog appears instead of the Great Pumpkin, Sally melts down in the pumpkin patch. Afterward, Linus and Charlie Brown have this exchange:

🎃 Linus: You've heard of the fury in a woman scorned, haven't you?

🎃 Charlie Brown: Yes, I guess I have.

🎃 Linus: Well, that's nothing compared to the fury of a woman who has been cheated out of tricks or treats.

If trick or treating is a custom near you, which phrase do you hear most often? (And where? — if you're comfortable sharing a location)