A Fairy Godmother is an interesting trope; it's barely been used in fairy tales at all, and yet we all think of them as ubiquitous to the point of parodying them mercilessly, even though the parodies far outweigh the serious portrayals. In fact, the concept was made as part of a satirical "Mother" class in Dragon Magazine #238.
But I like the trope unironically and like all things pink, sparkly, sugar-sweet, and cute. So I'm going to literally take a joke too far and run with it.
In case you somehow don't know this archetype, the Fairy Godmother is a fairy (or magician) with magical powers that acts as a parental figure to a young protagonist, much like a literal godparent. A Fairy Godmother is a creature of good fortune, hope and love, and reward for the innocent and the downtrodden. There do exist, however, Wicked Fairy Godmothers. They spite and harm children, but they still possess a warped sense of nobility or even love under their evil. When they curse and cast calamity, it is to punish the inhospitable, the hard-hearted, and the misbehaving. They stylize their victims as moral lessons to others to keep walking the straight and narrow, even if their lessons are "Don't snub someone from a party or they'll murder your daughter." Manners are important.
Hit Dice, To-Hit, Proficiencies: as Magic-User
Saving Throws: As Halfling
Experience: As Elf
Prime Requisite: Charisma
Spellcasting: Fairy Godmothers cast spells as a Magic-User of their level, with the following differences. They have no need for spellbooks (use 3rd Edition-style Sorcerer rules if you prefer), and all parameters are determined by their Charisma instead of Intelligence. Additionally, if you have access to them, you may learn Witch spells as well as Magic-User ones. If you don't have access to them, allow drawing from Cleric/Bard/Druid spells that don't reference the divine. In any case, Fairy Godmothers cannot learn or use any spells that harm or hex. Wicked Fairy Godmothers, conversely, cannot use spells that help or heal. Additionally, they can craft Magic Items as a Magic-User and Witch of their level.
A Spoonful of Sugar: A Fairy Godmother is someone who cares for children. It's part and parcel of who they are. A Fairy Godmother cannot advance in levels unless they are currently matron to a child. A Fairy Godmother may choose one child (or all children from a single family), and is able to perfectly Scry on them at all times. The spells and abilities of a Fairy Godmother always succeed on their Godchildren, and are doubly effective if the Godmother wishes them to be. Children can include adolescents and particularly innocent and naive young adults. Princesses very commonly have a Fairy Godmother for their entire lives, and a child having multiple Fairy Godmothers is not unheard of. A Fairy Godmother can technically change her Godchild at any point, but unless they're the type who moves from home to home, fixing up broken families and the like, this is just a heartbreaking sort of thing to do.
Knit with the Needles of Fate: When serving as a midwife, the Fairy Godmother miraculously guarantees the good health of a newborn child, sparing them even from stillbirth. In addition, a Fairy Godmother can read the destiny of any infant she delivers or cares for, functioning as if they cast Commune at three times their level, though only in regards to seeing the destiny of the child. After doing this, the Godmother may Bless the child's life. This blessing can be anything, equivalent to making a chosen ability score set to the racial maximum, the use of a 2nd level spell ability 3/day, or some other powerful but subtle effect such as "May they always be kind, and have the means of doing right", or "May they never want for wealth and warmth, in home or heart," or even "May they love everyone and be loved by all in kind." This is a Wish-level ability that permanently alters the nature and destiny of the child.
A Few Of My Favorite Things: A Fairy Godmother of 5th level or higher can produce objects freely, and can be assumed to have any mundane object they desire in a bag or on their person, and can withdraw them with comical disregard of spatial dimensions. These objects are magical creations, and as such do not have any genuine monetary value. Not even fake coinage can be produced, as the objects are very fine and very authentic, but simply are aesthetically pure expressions of utility or decorum. These objects cannot be sold, either, and may only be freely given. However, you can only give gives to each person once a year, else the previous object will be destroyed by karmic happenstance. At least one Fairy Godfather makes a point of giving gifts to everyone, everywhere, every year...
Additionally, a Fairy Godmother can produce a Magic Item with this ability with more restrictions. They can only produce a single Magic Item, period. Any second item immediately destroys the first, and consumables cannot be produced. The Fairy Godmother does not need to meet the item crafting requirements for the item she conjures, however, she may not benefit from it. This Magic Item must be immediately gifted to one of their Godchildren. The Godchild can keep it if they lose their status, but they must be their Godchild at the time of receiving the gift.
Bibbidi Babbidi Boo!: A Fairy Godmother of 10th level or higher is no longer merely what they were. If they were a mortal practitioner, they have ascended into being as a fey. If they were a genuine fairy, they have gained a true soul through having loved and been loved by children. From now on, the Fairy Godmother counts as either humanoid or fey entirely situationally, when it would be beneficial. She no longer suffer the drawbacks of either type of being. She no longer ages, and if she looked old already, she has aged beautifully, gracefully. She will live endlessly, her body never tiring as a mortal's as long as her life is filled with the very stuff of youth. If she did not have them already, she also gains the following powers: Fly, Teleport Without Error, Enlarge/Reduce, Haste, Prestidigitation, and Invisibility, all at-will as the spells.
Finally, the Fairy Godmother receives a special magic wand that can substitute all material components of her magic, and her singing can substitute any somatic and verbal components. This wand, additionally, is a Wand of Polymorph Anything Into Any Other Thing, with unlimited charges, which functions only for her. The Polymorphing always has a temporary duration (Such as, until the clock strikes midnight), and can't be used on unwilling creatures whatsoever. Changed creatures do not receive the combat abilities of their new form either. Sorry, your spellcasting rules still apply.
A Dream Is A Wish Your Heart Makes: A Fairy Godmother of 15th level or higher is now a Big Deal. You can now grant bonafide wishes to your Godchildren. Every Godchild you ever have can have the benefit of Limited Wish three times in their lives, or one true Wish, or seven Minor Wishes (Like Limited Wish except it only goes up to 4th level spells). You control the intent of the wish, but you must abide by the Godchild's wording. They cannot do harm to others or produce mind-control effects, you cannot coerce the wish in any way, shape, or form, and every wish must have some sort of moral lesson built into them unless they are pure, unselfish, or are their dearly earned reward for a lifetime of hardship. By moral lesson, one does not mean the wish should punish the child, but that realizing the full benefit should require the Godchild learn something good from the experience, so as to grow character.
Anything Can Happen: A Fairy Godmother of 20th level can be mistaken for a god. She can speak with all things, freely speaking with the dead, all animals, plants, stones, wind and rivers. She can speak with inanimate objects, the sun and moon and stars, and they will all do her favors for kindnesses done in turn. Aside from this already amazing ability, a Fairy Godmother can borrow magic from the world around her. Once a day, a Fairy Godmother can drain spells in effect, or the charges of magic items, around her, and cast a spell without expending her own spell slots. The spell drains charges equal to its own spell level. For example, a Fairy Godmother could cast a 7th level spell by dispelling a 3rd level spell on an ally, disenchanting a 2nd level potion, and draining two charges out of a staff. At some specified time, such as the stroke of midnight or the rising of the sun, the borrowed charges restore to their original places, even if it means restarting a dispelled spell effect, which would pick up its duration where it left off. An unexpected quirk of this ability is it always leaves a physical trace of the spell it was used to cast, such as a glass slipper...
Code of Conduct: Like a Paladin, there's certain rules for how a Fairy Godmother must behave, if she wishes to be practically perfect in every way. Unlike a paladin, she won't lose her abilities if she merely falls short of this sometimes; there's always room for improvement, after all. Only a rejection of the values below will cause one to become Wicked:
*Must have a cheery disposition
*Rosy cheeks, no warts
*Play games, all sorts
*Must be kind and witty
*Must be very sweet and fairly pretty
*Take your godchildren on outings and give them treats.
*Sing songs, bring sweets
*Never be cross or cruel
*Never give children castor oil or gruel
*Love your godchildren like a son or daughter
*Never smell of barley water
*Don't scold and dominate, too
*Never give your godchild cause to hate you
SIDEBAR: Princesses and Fairy Godmothers
The innocence of a Princess and the motherly love of a Fairy Godmother have more in common than one would think, even bearing in mind that the two always find themselves hand in hand in destiny's road. In the chance that a Princess reaches adulthood and loses their innocence, but does not lose their incorruptible, saintly purity of heart, they may trade their levels in the Princess class to immediately become an equivalent Fairy Godmother. There are some benefits to this; a Fairy Godmother that is a former Princess retains her Healing Affections, Too Fair to Kill, Friend to Nature, and Mystical/Miraculous Song abilities, though these no longer advance with their new level progression.
SIDEBAR: Wicked Fairy Godmothers
A Fairy Godmother that does not love children for who they are but only what they could be, or who sees children as a means to a moral point unto themselves. They are those who are monsters who prey on children so that those beyond their reach can be better for the fearful lesson. They function as a Fairy Godmother, save for the following exceptions: Firstly, they have no Code of Conduct, and can be right awful nannies and wicked old witches. Secondly, their spellcasting cannot include spells that help and heal.
Spoonful of Sugar is replaced by Brimstone and Treacle, which otherwise functions the same, but offers Godchildren no saving throw on hexes, harms, and curses set upon them, unless the child is a Princess.
Knit with the Needles of Fate becomes By the Prick of a Finger, which functions identically save that a child they midwife for will always have some sort of feytouched handicap or deformity. Additionally, instead of blessing the child, they may curse them. This can even go upwards as to curse a child to die in a certain way. These curses are Wish-level tragedies.
A Few Of My Favorite Things becomes Poor Unfortunate Souls. The limit on the gifts they produce is removed, but now they are Deals. A Deal requires the subject to trade something to you, such as their soul, their voice, their most prized possession, or whatever fey bargain you can manage. The deal must hurt. No "I'll give you this Staff of the Archmagi in exchange for your toenail clippings" bullshit.
A Dream Is A Wish Your Heart Makes becomes Friends on the Other Side. Your wishing ability functions like Poor Unfortunate Souls, trading wishes for painful deals. However, there is no limit on how many wishes you can grant, so long as someone is stupid enough to pay.
Anything Can Happen is replaced by Maleficence. Should you ever be brought to 0 HP, you can permanently sacrifice anything to become a horrifying dragon and everything that entails, forever becoming a terrible creature of unfathomable darkness and arcane might.