'The Flash' Drops Starro the Conqueror Easter Egg in "Subject 9"

This week's episode of The Flash had several fun Easter eggs, but there was on in particular that not only tied back to Wall West's adventures in Blue Valley, but the Justice League's first-ever battle in comic books.

Spoilers for "Subject 9," the fourteenth episode of The Flash's fourth season.

In "Subject 9", Team Flash is trying to figure out which bus meta The Thinker will go after next and that leads them to Izzy Bowin, an aspiring country musician who just so happens to be the Arrowverse's gender bent version of the classic comic book villain The Fiddler. However, as the team does their research on Izzy which leads them to the tour schedule on her website, there's another comic book villain referenced -- Starro the Conqueror, an alien being of immense power.

A careful look at the musician's website reveals that Izzy's Blue Valley tour stop was cancelled and a blog entry noted that the reason for the cancellation was "some sorta starfish situation." That starfish situation is a reference to Wally's (Keiynan Lonsdale) time in Blue Valley where he had taken on the villain, telling Barry earlier this season that "self-reflection and a battle with a starfish from outer space gives you perspective."

For those who aren't familiar with this intergalactic starfish, Starro the Conqueror is a member of the Hatorei species who used their innate psychic abilities to gain control of a Star Conqueror Motherstar in the distant past and who uses the Starros as his instrument of conquest. He has faced the Justice League over and over again, and in the 31st Century even took over a large chunk of the universe and became a recognized power.

While Starro hasn't been seen on screen in the Arrowverse, the villain has appeared on television before. Starro appeared in a brief cameo on last year's DC sitcom Powerless where he was killed by Green Lantern...and splattered all over the window of Emily Locke (Vanessa Hudgens.) As for the fate of Starro on The Flash, that hasn't been revealed, but tonight's nod was a nice way to tie in Wally's Blue Valley adventures, even if Kid Flash has left Central City for the Waverider on Legends of Tomorrow.

The Flash airs Tuesdays at 8/7c on The CW.