Tonight is the night that kids go around houses and ask for candy.  In Ontario and I do believe most of North America kids say, "Trick or treat".  This can then be followed by any number of clever limericks, the one from my day included,
Not too big.
Not too small.
Just the size of Montreal.

Which just goes to show how things have changed because Montreal used to be the biggest city in Canada and immediately indicated something REALLY REALLY big in any limerick.

In Winnepeg, they say 'Halloween Apple" which is sung out in a G chord.  I had never heard of this before until a Winnepeger told me about it and even then I thought he was pulling my leg (until I confirmed with a second Winnepegonian.  The second 'Peger friend told me the limerick for Halloween Apples but I cannot remember what it is.

The whole Halloween apples thing seems like the best kept secret in Canada because I can't even find references to the limerick on Google.