Why are there so many Sci-Fi actor appearances in Arrow?

Question

In Season 1 of Arrow, I've noticed an unusual number of appearances of actors that are well-known for their roles in Sci-Fi shows.

There's:

• John Barrowman, known for his role as Captain Jack Harkness from Doctor Who and Torchwood
• Paul Blackthorne, known for Harry Dresden in Dresden Files
• Alex Kingston, known for River Song in Doctor Who
• Seth Gabel, known for Lincoln Lee in Fringe
• James Callis, known for Gaius Baltar in the new Battlestar Galactica

And likely more. (I've not finished watching Season 1 yet!)

Is there an explanation for this beyond just the "brand equity" these actors bring to the show? I normally don't recognize this many in show that's not that kind of science fiction. None of these actors are known for comic-related roles.

(I'm not familiar with all the workings of show business, but my hunch would be something like these shows sharing production staff, or someone involved in the making of the show being a "fan" of those shows, or friends with the actors. In a similar question I had about guest appearances, there was a surprising promotional explanation.)

Answer 1

Since Arrow is based off of a comic book property, it generally falls into the realm of "sci-fi genre" TV show. It's very common for actors in that genre to appear in other genre shows, partly for the name value, and partly because you see the same sets of writers/producers popping up behind the scenes as well. They get to know actors they like and tends to being them along to new projects.

For example, besides Arrow:

• Paul Blackthorn (Det. Lance) and Coulton Hayes (Roy) did an urban fantasy show together called The Gates
• Summer Glau (Isabel Rochev, you haven't met her yet) has been in lots of genre shows, best known for Firefly/Serenity and The Sarah Connor Chronicles, but also The Cape, Dollhouse, and Chuck among others.
• Alex Kingston was in the short-lived Flash Forward
• Seth Gabel is one of the leads in Salem

More than most other genres, people who watch science fiction shows seem to get very excited to see actors they already know popping up in other shows. It also seems like many of these actors seem to take a lot of joy and pride in doing genre shows. My personal opinion is that it's rare to find an actor that's really good at doing a sci-fi role and likes the "convention scene" enough to cope with it, so when these actors come along, they tend to show up a lot.