1) Since it’s a pretty major plot point that these characters were born in 2000, all of the actors here were born within a year of that. Regina Daniels and Lucas Jade Zumann were born in 2000 exactly, Kiernan Shipka in 1999, and Xolo Maridueña and David Mazouz in 2001. (I couldn’t find an exact birth date for Kyra Ynez Siegel, but several articles including the one linked above mention she was 10 in December 2009, so she was likely born in 1999 as well.) 

2) It was really important to me to cast an actress who’s actually blind (or at least visually-impaired in a significant way) to play Flicker, which wasn’t easy since blind actresses aren’t exactly common, let alone blind teen actresses of the right age. Luckily I was able to find Kyra Ynez Siegel, who was the first actually visually-impaired actress to play Helen Keller on Broadway and is exactly the right age. She’s also an extremely adorable and awesome person, as you can see if you check out her YouTube channel!

3) Similarly, I wanted to cast an actual Nigerian-American or (as is the case with Regina Daniels) Nigerian actress for Chizara rather than any black actress, since the story makes a point of designating her family as specifically Nigerian.

4) I kind of wanted to cast an actor of color as Thibault to add a bit more diversity (of the canonically white Zeroes, he seemed like the most obvious choice since Kelsie risks falling into stereotypes because of her criminal family background, and Kyra Ynez Siegel was really the only visually-impaired actress of the right age I could find for Flicker), but... Lucas Jade Zumann is just so perfect for Thibault. He’s even been a practicing Zen Buddhist since he was five! And anyone who’s seen him as Gilbert on Anne with an E (which he’s great in BTW) can tell you he’d bring exactly the right mix of vulnerability and charm to the role.

5) On the subject of diverse casting: David Mazouz arguably is an actor of color, since his father is Tunisian-Jewish. However, as a Jewish person myself, I can tell you that racially categorizing Jewish people can be complicated since we tended (by necessity, sadly) to migrate so much and obviously I don’t know his entire family history. And of course, some people would argue that Jews, and particularly Sephardic Jews like David Mazouz, are non-white by definition, so... let’s just say David Mazouz’s racial identity is Complicated and leave it at that.