But Why?

We've hit it...the "but why?" stage.
"But why? Mummy?"
At this point, I'd like to add my own "but why?" to the author of Clifford the Big Red Dog.  To those who are yet to discover the joys of Clifford; he's a big red dog and when I say 'big' I mean, yes, as big as a house.  So Max raises a very good question, "Why?"
"Why does he grow so big?  Why is he the size of a house? Why does he need a crane to lift him out of his owner's apartment?" And here, I'll point out, we are reading this book out-loud in the library, the public library. 
'But why?' Good question. I should have checked it out sharpish and taken it home to read in the privacy of Max's bedroom. But instead, I can feel people lingering in the aisles near us, waiting for my answers.
Inconceivably the runt of the litter suddenly grows and grows, bigger than a horse; yes, bigger than a digger.
"But why?" says Max again.
"Well, let's read to the end, and maybe, we'll find out."
I can hear the browsers nearby shifting their weight. Instinctively I know, there is no answer, no salvation for me on the last page.
"He's about the size of a very tall tree, but a bit bigger." I approximate for Max.
"But why?"
I think Dr Seuss wrote a book about a goldfish who was given too much fish food, and briefly ended up in a swimming pool before being shrunk back to his real size.  I'm hoping Clifford's author will offer some sort of explanation, and if not, a return to normality, but no, there's nothing.
The book ends. The dog is still big, very big, and red.
"Can we take this book home?" Max asks.
Think of me, we've got it for three weeks.