Everyone who wants to trade pussycoins can use https://etherdelta.com/#0x70d0b338db31125f2324cdfdad10b096a6697c99-ETH

If you require a verification fee which is not auto-refunded, its not a airdrop. Just a ICO with requirements.
If you want to avoid wasting GAS, you can make the user call the contract (with a special value, that is initially stored hashed as a proof he posted and that)