The Red Mushroom is a forageable item typically found in the Secret Woods or the Mushroom Cave, if the latter has been selected on the farm. It can also appear in the Mines, particularly on floors that have a red or purple hue. This item can be hazardous to health if consumed, as it is poisonous, but it is valuable in crafting and as a gift for certain villagers who appreciate its rarity and unique properties.
The item ID for Red Mushroom is 420
This ID will work on PC/Mac (Steam), PS4, PS5, XBOX One, and Nintendo Switch.
Spawning items in Stardew Valley is a little unsual and is not done with commands. You will need to utilize what is called a cheat to set your character's or animal name to the item id. To do this you cannot use just the item id, you will need to surround the item id with brackets. Ex. [420]
Spawning Using the Animal MethodTo spawn Red Mushroom while using an animal, you will need to head over to Marine's Ranch and purchase an animal. Once you have have an animal chosen, name the animal with the item id with brackets like this [420] and you will receive the Red Mushroom item. This method can be done using an existing character and is convenient but will cost some gold every time you want an item.
Spawning Using the Character MethodTo spawn Red Mushroom while using a character, you will need to create a new character and name it with the item id with brackets like this [420]. You will then receive the Red Mushroom item when you speak to a villager. This method is easy and free but cannot be performed on an existing character and you will be stuck with that name unless its edited.