I strongly advise against making trading decisions based solely on humorous or anecdotal information. Financial markets are complex and influenced by numerous factors.
That said, here are some lighthearted, fictional reasons "why" you might consider shorting GBPNZD (please don't actually do this!):
The All Blacks Curse: The New Zealand rugby team is simply too good. Their dominance is inevitably causing the Kiwi dollar to soar while the Pound cowers in fear.
Sheep Overpopulation: New Zealand has an absurdly high sheep-to-human ratio. These woolly creatures are secretly manipulating the NZD higher with their psychic powers.
Hobbit Home Prices: The rising cost of living in Middle-earth (New Zealand) is causing a property bubble, which will inevitably burst, dragging the NZD down with it.
Marmite Shortage: A global Marmite crisis (a staple in the UK) will lead to widespread panic and a plummet in the Pound.
LOOOL