The Stalker is a mob from a Minecraft Fangame: Pixel Gun 3d, It is a six legged green monster with a huge red mouth, it also has a black dot in the middle, which resembles an "eye".
Like Zombies and Skeletons, This mob has serval variations, The Yellow Stalker, The Armored Stalker, The Crypt Stalker and Even The fanmade Iced Stalker, There's also The Giga Stalker, The Stalkling and Even The Candelavra Stalker, this mob will go against Iron Golems, Just like Zombies, Skeletons, Illagers and Breezes.
This monster is only found at night in the savanna biome, As well as the City, Bridge, Prison, Area 52 and Village Locations from once again, Pixel Gun 3d, This mob attacks the player by bashing its head to Him/Her.
Due to Issues with Caseoh (Notch, The Ugly Former Developer of Minecraft who is a transphobe and neo nazi), They became what we know Today, Same Reason for The Slimeslug and Its versions.
The Mimicked Candelavras could be The Candelavra Stalker.