Essentially, this was actually two hour-long panels so I'll go in order. First up was Arrow. The panel included Marc Guggenheim, Andrew Kreisberg, David Ramsay (John Diggle), Paul Blackthorne (Quentin Lance), Katie Cassidy (Laurel Lance), Stephen Amell (Oliver Queen), Emily Bett Rickards (Felicity Smoak), Colton Haynes (Roy Harper), Willa Holland (Thea Queen), John Barrowman (Malcolm Merlyn), and Greg Berlanti. Both panels were hosted by actress, TV personality and professional fangirl Aisha Tyler.
They kicked off the panel with some discussion about where the season has been going and how dark it's been. Stephen noted, "It has to get worse before it gets better." There was some joking about how at this point everyone knows who Oliver is "Except the detective!," said Paul Blackthorne. Even fans have noted how Det. Lance managed to figure out Roy's secret identity as Arsenal because of his red hoodie but hasn't connected the green arrow with Oliver who ran a club called Verdant and dated his daughter(s) for years.
In regards to where we left off before the mini hiatus, Stephen acknowledged that Oliver would have some decisions to make and that the idea of becoming the next Ra's Al Ghul holds some appeal for Oliver. Though he did note that "If Oliver says no there will be dire consequences." John Barrowman also commented that he wonders if Oliver becoming Ra's will wipe the slate clean for Malcolm or create a new set of complications.
John Ramsay on Diggle: He's not like Oliver in the sense that he believes he can have a family and be a crime fighter. "He's reconciled his island"
Willa on Thea joining Team Arrow: Initially Thea wanted to learn to fight to protect herself but now that she has these skills "she could" join Team Arrow and hold her own.
Emily on Felicity and Laurel's newfound friendship: "I like that Felicity has Laurel. I like this ... (To Katie) I like you..."
Also we learned that Emily raps to memorize her lines and Willa got caught up in a moment and licked Colton's face while he answered a question about where Roy and Thea are going towards the end of the season.
The Flash panel was also chock full of stars. It included Andrew Kriesberg and Greg Berlanti again, as well as Carlos Valdes (Cisco Ramon), Danielle Panabaker (Caitlin Snow), Tom Cavanaugh (Harrison Wells), Grant Gustin (Barry Allen), Jesse L. Martin (Joe West), Candice Patton (Iris West), and Rick Cosnett (Eddie Thawne).
The panel opened up with Grant discussing how being on Arrow allowed him to develop Barry as a character before he became a superhero and how invaluable that experience was. There was a lot of focus on the science of The Flash with regards to what we've seen so far as well as what's to come with time travel. Kriesberg noted that the science is grounded in reality but mostly not real but Berlanti did state the show is careful to establish rules for their universe and not break them once they do.
The Flash universe also focuses on the importance of mothers and Kriesberg did tease that Mrs. West would come up in conversation this season though Berlanti stressed that Iris' mom wouldn't be addressed directly until season 2. When asked to speculate about the implications of Barry saving his mom and changing the past, the cast discussed how that would affect the family Barry has built with Joe and Iris and Jesse jokingly states that since Barry grew up next door they'd "still be cool." Also when asked about whether some of the other S.T.A.R. Labs members would be developing powers like their comic book counterparts Carlos said that this season was about Barry but that may happen down the line.
Candice on Iris not knowing Barry is the Flash: "[Not knowing] always adds a bit of excitement and mystery" and she added that it's fun being the Iris West or Lois Lane character. She did say that when Iris finds out that the only two men in her life are lying to her, it's going to be a big deal. (When she said the "only two men" Rick Cosnett playfully switched seats with Andrew Kriesberg)
On the metahumans in the lab: We will see them be fed and we will deal with the moral ramifications of the Flash team playing judge and jury.
Carlos on the importance of naming the villains: "I have to respect the naming, it's a calling"
Apparently watching Grant run on set is very amusing especially for Jesse. Rick is very excited for the audience to see where Eddie goes in the final third of the season. Also a young fan got up and recited Barry's monologue from the opening of the show. The entire cast gave him a standing ovation.
Overall, both panels showed the ease and friendship each cast has. They joked with the audience and each other. Aisha Tyler asked great questions which the producers and actors artfully dodged so as not to spoil us but the clips before the panel did give away some details so continue to read at your own risk.
DANGER SPOILERS AHEAD:
Arrow: When we last left Oliver he was being offered the role of Ra's Al Ghul and Stephen said that Oliver is interested in taking the position because he hasn't felt that he's achieved much as the Arrow. In the clip, we see an emboldened Det. Lance taking down Team Arrow's lair (they really need better security). Ray also discovers that Oliver is the Arrow much to Felicity's devastation and Roy and Thea are kissing again. We also see the Arrow and Black Canary fighting side by side and ... MAJOR SPOILER ... a not at all dead Shado shows up in an Oliver flashback.
The Flash: We see Eddie pointing his gun and shooting at two cops. He also talk to Iris about Barry ominously saying "Something has changed with you two and I don't like it". Reverse Flash is revealed as Harrison Wells to Caitlin and LAUREL tells Cisco she's Black Canary. Kriesberg also stated that we'll find out how Reverse Flash was able to "beat up" Harrison in episode nine. Barry says to Iris, "I still think about you and I know you still think about me" and we see Joe stuck in that sewer with Gorilla Grodd. Also Felicity will get her own nemesis (Walking Dead's Emily Kinney as the Bug Eyed Bandit). And Captain Cold and Heat Wave are taking another shot at the Scarlet l Speedster. Overall the last part of this season looks very dark. Even Felicity says, "I thought Central City was supposed to be the happy place"
*Edit* Added in the PaleyFest trailers for Arrow and The Flash