The first one I found is a salesperson selling some good items in the Castle of Tansicia (is that how you spell it?). Go to the room with the bridge. You can already see him. Do this:

1. Go behind the bar.
2. You should be able to walk into a wall behind there.
3. Make your way around into the room.
4. You can still talk to the person while you're standing on the ground.

Note: This second one is completely pointless, even though it's fun.

Haven't you always wanted to work at a hotel? Here's your chance! Just do this!

1. Go to the inn at Matango.
2. Walk into the wall on the left side.
3. Make your way around to stand at the counter!