Tip : How to tell if you've gotten all the Merrymakers

I discovered this by accident. If you open the Event menu, tap the tabs, then close it - if you've gotten all the Merrymakers the message that:

There are no Merrymakers left in your town!
But how long till more arrive?
will pop up. So if you do it and you don't get the message there are still Merrymakers roaming around your town.

The Railyard buildings will coax the message into working too, but only when the handshakes start popping up.