The Shamblers from The Last of Us Part 2 had big explosive bums in an early build of the game.
As spotted by TechnClub, Matthew Gallant, lead systems designer at Naughty Dog, shared a clip of what appears to be a test environment with Ellie in combat with a few Shamblers that have a very different appearance to their look in the final game.
As you can see in the video below, the Shamblers' bums were bright and appeared to explode and exert a gaseous acid.