Since he got his own spinoff show, The Flash has periodically dropped into Star City for cameo appearances on Arrow -- and Green Arrow has done the same on The Flash and DC's Legends of Tomorrow.
In next week's episode, though, it seems as though The Flash will make his briefest-ever appearance on the parent show.
Arrow executive producer Marc Guggenheim teased a look at the scene, in which The Flash is speeding through what appears to be a police station, leaving a Post-It Note on the computer monitor of a man who is preoccupied with a cell phone call.
We're going to take a big leap of faith and guess that Barry might not even have a line in this cameo, but that he's simply called in for the assist and appears in this one scene, which would likely take like 3 seconds. If that's the case, you have to wonder of Grant Gustin even shot anything or if they used digital recreations of Barry -- as The Flash sometimes does when doing the high-speed sequences.
In the episode, H.R.'s (Tom Cavanagh) past catches up with him when a bounty hunter with vibe powers named Gypsy (guest star Jessica Camacho) arrives in Central City to bring him back to Earth-19 to stand trial for his crime. It turns out inter-dimensional travel is illegal on their Earth. H.R. surrenders but when Barry (Grant Gustin) and Cisco (Carlos Valdes) find out that H.R.'s only hope would be to challenge Gypsy to a fight to the death, they intercede and Cisco offers to fight Gypsy instead.
Harry Jierjian directed the episode with story by Benjamin Raab and Deric A. Hughes and teleplay by Zack Stentz.
Given the fact that the A plot doesn't seem to relate to police or law enforcement much, we have to wonder whether this might be connected to Diggle's court martial.
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Arrow airs on Wednesday nights at 8 p.m. ET/PT on The CW. This episode, "Dead or Alive," premieres on February 1.