Ta-da! Chocolate bars now grow on trees... at the very top of really, really tall trees (like Sequoia height), that is.

I wish I had the ability to fly.

You now do, but you can only fly a few inches above the ground.

I wish I had expandable bookshelves.

Shazam! Your bookshelves have just expanded... so far and so fast that they've smashed through the walls of your room and are still growing...  

I wish I had a packet of Tim Tams* that never runs out.

(Delicious chocolate biscuits from Australia. Certain others here may recognise the reference to a TV ad campaign from years ago. )

Your wish is my command. *poof* You now have an eternal packet of Tim Tams. Unfortunately, they are all contaminated with E. coli and could make you deathly ill if you consume them.

I wish I was taller.

Wow! Your wish is granted. You have grown so tall that you have to bend your head to stop it bumping against the ceiling.

I wish I was younger.

Congratulations, you're now younger, much much younger... in fact, you've just turned back into a newborn infant, and it may be a few years yet before you get around to doing anything more complicated than re-learning to walk, talk, feed yourself and so on.  

I wish I could teleport instantly to any location of my choice.

It looks like it's your lucky day. You can go anywhere in the world you want. The catch is that the teleporter has no oxygen and requires hours to take you to your location. Better learn to hold your breath for a long time.

I wish I were smarter.

Congratulations, you are now smarter! However, becoming smarter only makes you aware of all the things you still don't know or understand. And so the cycle continues....

I wish I was healthier.

Poof! You are now the healthiest person in the world and are now immortal. Now you shall live far beyond the lifespan of any other human being and will outlive all of those who are familiar to you.

I wish I could visit any place in the country I want.

You can now visit any place in the country you want, but you can only stay there for 30 seconds at a time.

I wish I could sew anything I wanted right the first time.

Ta-da! Now everything you sew comes out perfect the first time... but the magic stitching only lasts for 24 hours before dissolving into the ether.

I wish I could visit Narnia!

Roar! Your wardrobe has become a portal to another world, but unfortunately it is Charn.

I wish I had stronger muscles.

Shazam! You are now the strongest hobbit in New Zealand (and probably the world)... so strong, unfortunately, that you inadvertently break every object you pick up.

I wish my housework would do itself.

Oh, how reasonable is your desire! Your housework does do itself. However, it is almost impossible to find anything afterwards, in the nice, tidy, clean home you now have.

I wish that I no longer had to submit a tax return by the 31st of October.