This kind of deal has been posted before, basically you make a $50 donation to Child Cancer Foundation and you can choose to receive a LEGO Owl (40497). It looks like there is also a LEGO Brickheadz Poodle as an option as well.
From the Instagram post:
WHO wants a special Halloween Owl LEGO® set? 🎃
No tricks, here. Simply donate $50 or more online and select 'LEGO® Owl' as your reason for donating!
Thank you LEGO® for donating these packs. It's a generous treat indeed. 🦉
T&Cs:
1. Donation must be at least $50 and made on our website: www.childcancer.org.nz/donate
2. 'LEGO® Owl' must be selected as the reason for donating on the donation form
3. Online bank transfer donations will not apply
4. LEGO® set recommended for ages 8+
5. New Zealand addresses only
6. Offer available while stocks last
7. Donations for LEGO® sets will not qualify for tax credits.
Remember to submit to IRD to get a 33% tax credit claim too! (Can be refunded to your bank)