Large, yellow eggs were present in the Upside Down, coated in some kind of webbing. The Demogorgon hunkered over these eggs, seemingly feeding off them. It is currently unknown what hatches out of these eggs.
When Joyce Byers and Jim Hopper entered the Upside Down to search for Will Byers, Hopper found and briefly studied a broken eggshell near Castle Byers that appeared hatched; it was hollowed out and cracked open at the top.
Behind the scenes
Aaron Sims Creative created the concept art for the egg. The company Fractured FX, who made the prosthetics for Will's fake body and Barbara's corpse, created the prosthetic for the egg as it was seen in "The Upside Down".
In the closing moments of "The Flea and the Acrobat", Nancy enters the Upside Down and witnesses the Demogorgon hunched over something, appearing to feed off it. In an interview, visual effects artist Aaron Sims implies that the Demogorgon was feeding off an egg in this moment. Despite this, close inspection of the scene suggests that it was instead feeding on the wounded deer Nancy and Jonathan found earlier in the episode. 
- "Chapter Six: The Monster"
- "Chapter Eight: The Upside Down"
- "Exclusive ‘Stranger Things’ Art Reveals ‘Upside Down’ Secrets and Barb’s Alternate End" ScreenCrush. August 22, 2016.
- "The Egg we created for STRANGER THINGS!" Facebook: Fractured FX. August 19, 2016.
|The Upside Down|
|Locations||The Upside Down • The Gate • Hawkins • Hawkins National Laboratory • Public Library • Portals • Hawkins Middle School • Hawkins Tunnel System|
|Entities||D'Artagnan • The Demogorgon • Demogorgon (species) • The Flayed • Hospital Monster • The Mind Flayer • Russian Demogorgon • The Spider Monster • Hawkins Tunnel System • Vines|
|The Flayed||Billy Hargrove • Heather Holloway • Bruce Lowe • Tom Holloway • Janet Holloway • Doris Driscoll|
|Visitors||Joyce Byers • Will Byers • Eleven • Steve Harrington • Dustin Henderson • Barbara Holland • Jim Hopper • Max Mayfield • Bob Newby • Shepard • Lucas Sinclair • Mike Wheeler • Nancy Wheeler|
|Miscellaneous||Upside Down Egg • Dungeons & Dragons • The Void • The Keys|
|Articles may contain spoilers.|