Toby's Rules

Can you spot the rules of the poem?

Leave a comment if you can spot any of the 5 rules this poem follows to create its structure. Bonus points if you can tell me the line where I broke the rules. Double bonus if you tell me why I broke those rules in that line.

There was once a little dog named Toby.
He had curly white fur oh so fluffy.
Bichon with a big personality.
Should I say, a big do…