Cast Spell is a interaction only available to Sims who own wands[TSMM] and Witches, as well as is tied to a Secret Skill. This interaction is usually accompanied by multiple other interactions know as spells, these help witches use their magic to manipulate their surroundings. Cast spell can be used on multiple things such as themselves, other Sims, objects, or any surface.
The Sims: Makin' MagicEdit
In The Sims: Makin' Magic, Sims can only cast spells if they have a magic wand, which is accessed when the Mystery Man appears with a box containing a wand as well as many other magical objects. Sims can then charge their wand with a spell and the "Cast Spell" action will appear to which a spell will be casted depending on what spell they charged the wand with.
The Sims 2: Apartment LifeEdit
In The Sims 2: Apartment Life, Sims can only cast spells if they were granted witchcraft via another witch who knows the spell "Magus Mutatio". Witches can then cast spells which they learn from their spellbooks to which they will make a wand appear and cast the spell.
The Sims 3Edit
In The Sims 3 Store, Lady Ravendancers Goth's Book o' Spells is an object which can be bought for 395 Simpoints. Sims can learn a set of spells and after they learnt the spell, they can finally cast the spell. However, casting spells can fail and to stop this is by regularly review spells the Sim has learnt.
In The Sims 3: Supernatural, Sims can become witches, however, they cannot learn the "Cast Spell" interaction as it requires getting higher in the spellcasting secret skill, which is achieved by the "Playing with Magic" self interaction witches have. When they reach level 2, learning the "Fire Blast" and "Ice Blast" spells, then witches can unlock the interaction.