A favourite from my youth. It was great to come back here again. The best interaction was not a specific event, but instead 'snappy hour', where keepers would wander around with some of the reptile park's inhabitants. You even get the chance to hold a python.
Wildlife Sydney Zoo - Cassowary Encounter
While the Zoo offers a host of activities throughout the day, the most exciting for me was the chance to interact with a Cassowary, and going behind the scenes to feed them. Cassowary Encounters are held at 12:30pm every day, though places are limited, so it's best to inquire if you are going on the weekend.
Manly SEA LIFE Sanctuary - Shark dive Xtreme Don't let the word spelling put you off from this fascinating activity. This experience will train you in using diving equipment, and then give you the chance to swim with both Sea Turtles and Grey Nurse Sharks. While it is expensive, $224 for someone who has never used diving equipment before, it is the only place you can go to experience these animals without a barrier. If you like a bit of glass between you and your ocean attractions, there is also an $85 offer at Sydney Aquarium.
Taronga Zoo - Owl Encounter Taronga offers a range of exciting animal encounters, from daily reptile encounters, to the opportunity to feed a giraffe, or waddle with a penguin. The most exciting, though, is the owl encounter, where you get the opportunity to take one of these birds on your wrist, and really get up close. The penguin encounter will also gain some 'aww's from fans of cute animals.
Featherdale Wildlife Park- Everywhere, all the time Featherdale is a great place, as it allows many of the animals to roam. Food for kangaroos is readily available for purchase, allowing you to feed everyone's favourite hopping marsupials - there are also wallabies if that is your particular favourite. Vanessa has done a full write-up of Featherdale here
As for the best place to snuggle up to a Koala? Any of the above! Save the Aquarium of course. The four other places all offer the chance to meet a koala, so if that is your Australian nature dream, then take heart - there are many opportunities.