I’ve commented the following before:

That’s the fun part of the far side.

When you don’t immediately get it you have to wonder:

1. Is it a reference to something at the time that’s not within my lifetime/country’s zeitgeist?

2. Is it a play on an idiom or common cliche?

3. Is it literally nonsense and absurdity for the sake of it?

4. Am I just a big dummy?

I think this time it’s 3.

There’s a giant being outside the window breathing at a volume that the lady believes is her husband coming down with a cold. They’re oblivious to the fact that the giant being is there. That’s the intended humour -it’s just absurd.

(It’s never 4)