Scarecrows are mobs that spawn in the plains.
Scarecrows are noticeably taller than the player. They have long arms connected to their body which is most likely a wheat bag and a Pumpkin head with one green glowing eye.
When hostile they hold a scythe.
Scarecrows can be found standing in the Plains.
During the day
When found during the day Scarecrows are passive. They will stand with their arms wide open and won't attack even if hit by a player.
During the night / In the dark areas
Scarecrows no longer exposed to the daylight turn hostile. When nearby a player they'll swing their scythe delivering a deadly blow. It can be avoided by keeping a distance from them as they are slower with their weapon equipped.
It's not possible to tame a wild Scarecrow. However, a player can summon a Scarecrow follower by placing Jack o'Lantern on top of 2 hay bales and right-clicking in the middle with an Undying Heart. Summoned mob is not hostile towards the player and is following them like a tamed wolf (even when exposed to daylight).