The Oasis at Animal Kingdom is the first area of the park you enter, so there tends to be a character or two hanging around there to welcome you. There are no attractions here that involve characters and there are no specified character greeting areas. Even so, there's a good chance Goofy or Pluto (on safari, of course) will come by to say "Hi."
There are two entrances to the Oasis at Animal Kingdom. The first is the main entrance to Animal Kingdom. Once inside the gates, you are in the Oasis. The second is a bridge from Discovery Island. This is the only way to access the rest of Animal Kingdom, and it is also the only way to exit the park.
The layout of the Oasis at Animal Kingdom is fairly simple. It is the smallest of Animal Kingdom's lands, and it is where you enter the park. Once inside the entrance guides, the Rainforest Cafe and some park services are to your left. Garden Gate Gifts is to your right. Directly ahead are The Oasis Exhibits. Past the exhibits is the bridge to Discovery Island and the rest of Animal Kingdom.
There is one public restroom area in the Oasis at Disney's Animal Kingdom. It is immediately to your left after entering the Animal Kingdom entrance gates.