Currently, there's 23 pets on the list and this is not only an uneven number, but also sounds like "He who hatches no nuts" in chinese The only solution can be adding a special nuthatch to the quest list !
But then, the number 24 reminds me of the show '24', starring Keifer Sutherland. As you may remember, the President on that show during seasons 1 & 2 was David Palmer. 'Palmer' contains 4 characters in common with 'plover'. Therefore, we need a special plover too. Once that is done, 25 has aesthetic appeal, being a quarter of 100. That reminds me of the quarter I used to pay for a Snickers bar the other day. I opened the wrapper and you know how candy bars sometimes have a little slogan on the inside? Yea, this one had one. It read: "UOR should totally have a special llama in the new Zookeeper quest". I'm sure we could all go on, drawing the obvious lines between numbers all the way up to 1000, but WHEN WILL THE MADNESS END!?