3e SRD:Creature Spells
From D&D Wiki
|This material is published under the OGL|
Some creatures can cast arcane or divine spells just as members of a spellcasting class can (and can activate magic items accordingly). These creatures are subject to the same spellcasting rules as characters are.
Spellcasting creatures are not actually members of a class unless their entries say so, and they do not gain any class abilities. For example, a creature that casts arcane spells as a sorcerer cannot acquire a familiar. A creature with access to cleric spells must prepare them in the normal manner and receives no bonus spells.