The actors in Firefly have since appeared in numerous other sci-fi tv shows and movies.
Note: The actors need not have recurring roles. A cameo is enough to qualify.
Assuming you want to discount anything that's Firefly-related, the winner is Con Man, Wash [ahem, sorry] Alan Tudyk's pet project. It has six of the main actors, although not all in the same episodes.
As of May 2016, second place goes to Castle, with 5 veterans:
Third place is a tie between CSI (oddly enough) and Justice League.
CSI: Crime Scene Investigation has had the following main Firefly actors, although definitely not in the same episodes. (Which means that the show doesn't come up if you do a "credited with" search on IMDB.)
The Justice League animated TV series has also had four of our actors doing voices:
Honorable mention: Buffy-verse has had four actors, but not in the same series. Nathan was in Buffy itself, and Summer, Adam, and Gina all appeared in the spin-off Angel.
5th place is a three-way tie between the aforementioned Angel and the video games Halo 3 and Halo 3: ODST, which both had Adam, Alan, and Nathan.
Looking at it from the actor's perspective, Adam Baldwin has shared the screen most often with his erstwhile co-stars, with 19 of his shows having at least one other Firefly alum. The person who has worked on the same shows as her co-stars the least is Jewel, with only 4 shows: Con Man, The X Files (Adam), Warehouse 13 (Sean), and Castle. The numbers are:
The Firefly mobile RPG features all of the original cast along with several of the supporting characters such as Niska (who will provide the players with a continuous stream of jobs and missions).
At the Firefly panel Thursday night of Comic-Con, the cast members announced they would be providing voices for Firefly Online, an upcoming mobile role playing game set in the ‘verse of the series. Fillion, Gina Torres, Adam Baldwin, and the rest of the main cast will lend their voices to the game, while Alan Tudyk will provide “multiple voices” for different characters. Given Tudyk’s experience voice acting in animated films — Wreck-It Ralph, Frozen, and Big Hero 6 — it’s no wonder why he’ll be providing more voices aside from that of his original character, Wash.
You may wish to note that the beta was launched a while ago, but the full game seems to be stuck in development hell.
