One meaning of "of course"

Here in North America, I'm pretty sure I've heard such usages.

NOAD defines the idiom of course as:

used to introduce an idea or turn of events as being obvious or to be expected

Contextually, that fits with the meaning you describe.

For example, someone might be talking about a chain of unfortunant events, and then insert of course:

I was already running late, and of course I hit every red light on the boulevard.

In this example, it's not so much that hitting every red light would be obvious or expected per se, but, in the context of the conversation (perhaps cued by a vexed tone of voice), one might use of course in the same sense as naturally, particularly with Murphy in mind. In other words, things were already going wrong – what else would you expect?

Given that the title is 'Tiptoes the Mischievous Kitten' the of course refers to the fact that Tiptoes will always be involved in whatever mischief is happening. It is not acknowledging the validity of the sentence on the page, it is acknowledging the fact that you, the reader, with your knowledge of plots and Murphy's Law, will fully expect Tiptoes to turn up and mayhem will follow. In fact you would feel very short-changed, in narrative terms, if Tiptoes slept the afternoon away and nothing happened.

I would use 'of course' in this way all the time (UK), in a humorous/sarcastic/ironic way, so I'm very surprised to hear you do not use it in Canada. :)