The mouse ran up the clock.
The clock struck one,
The mouse ran down
Hickory Dickory Dock.
What comes next?
Repeat the only verse until bored.
Hickory Dickory Dock The mouse ran up the clock. The clock struck two, The mouse said "boo". Hickory Dickory Dock. (etc. until four/no more)
Something else, to be explained in comments.
I'm not used to this song having additional verses, but that's how it's sung at local playgroups. Is this a recent development? A UK thing? A local thing?