There’s nobody really noteworthy until you pass Narrow Street, and even after that there’s just a bunch of random people standing around until you reach Passerby Analytics.  This place mostly exists for the sake of Tag Mode and other Wi-Fi things, though there is a Harlequin in here that you should speak to.  Talking to the people in Passerby Analytics will let you do things like set your personal greeting, get Statistician jobs that will garner you small rewards for passing by people with your C-Gear turned on while they’re also playing, and fill out a questionnaire.  You can get a Soda Pop by filling out the questionnaires the lady by the computer gives you, so if you can spare a couple minutes to do that you should go ahead.

After Oceanfront Road, the rightmost street in Castelia is Castelia Street.  Here you can see a lot of people running back and forth down the road, who will try to go around you when you directly encounter them.  The first building you’ll see here is the Game Freak building. The only floor you can really access here is the 22nd, but it’s an important floor all the same, containing the design team for the Pokemon games.  A Revive waits for you in the bottom-left corner, and you can also battle two trainers here- Morimoto, who has hair, and Nishino, who doesn’t.  They’re sitting at the table to the South with the music director, and you can battle each of them once each day.  Their pokemon levels will depend on how far through the game you are, as will the amount of reward money you get for winning the battles, so I’m not going to list levels and rewards here.

Battle: Morimoto
Opponent: Elemental Monkeys (Pansage/Panpour/Pansear or Simisage/Simipour/Simisear)

Battle: Nishino
Opponent: Clefairy/Clefable

Off to the right at the North end of the floor you can find the Game Director, who waits for you to fill up your Pokedex.  Make sure you remember to come back here later when you’ve seen everything you need to for the ‘dex.

Also on Castelia Street, to the left, you can find a vending machine outside the other enterable building.  This building is also small, containing only a few things of note.  A couple of people in the lobby are having a discussion about Critical Captures, something you’ll want to watch out for.  The upper floor is the 11th.  Here you can find a guitarist who passes you the TM for Rest and mentions giving her pokemon a Chesto Berry so that it will wake up immediately on using the move- a sometimes very useful tip.  After that there’s really nothing else in the building, so it’s time to move on.