OK you tech heads - here's the full SP on the nuts & bolts of Frilli's character and abilities.

OVERVIEW
Our campaign is based on the AD&D 2nd edition rules and is set in the TSR (now WOTC) Forgotten Realms.  My gaming pals and I have all been playing AD&D for so many years that the 2nd edition rules fit us like a pair of old comfy slippers so we have no plans to convert our gaming to 3rd edition as we just can't be arsed!  If it ain't broke.....  Our gaming style has developed over the years and we tend to use the rules that suit us and either modify or disregard the ones that don't.  We game for enjoyment as a leisure activity so we don't want to follow silly rules and dictates as if we're at work.  Pedantic rules lawyers' characters in the past have tended to suffer disproportionate amounts of serious injury and death courtesy of Dave P. our illustrious DM, until they have got the message.  We also much prefer a harmonious party without characters colluding, cheating or backstabbing each other so players found playing such characters are strongly persuaded otherwise.

FRILLI'S CHARACTER
Frilli started out as an idea for a fun character who was a complete change from my normally favoured strong, skillful and effective Elven Ranger types.  When I said I wanted to be as small as possible and preferably able to fly Dave suggested playing a Fremlin.  Frilli is a Fremlin player character straight out of the Humanoids Handbook with a few tweaks to make him more practical & fun to play.  He has the standard chaotic neutral alignment as I felt this would give me ample scope to have him do stupid, mischievous and contradictory things.  He tends to be slightly more courageous than standard to enable him to participate (to a minor extent anyway) in combat situations but he does get scared easily and makes a fear roll when appropriate.  He is most certainly not obnoxious or wingeing but can be pretty lazy.   If upset he may well sulk for a while but he doesn't clear off for days on end at the slightest insult as I'd soon get bored sitting there with nothing to do.  He does enjoy pranks but is careful not to upset the party too much as they are his protection & meal ticket.  Frilli is a self taught Mage/Thief by trade and it is through these abilities - or lack of them - that most of his role playing amusement is generated.    

Being extra planar means Frilli is immune to non magical damage like normal weapon strikes and large boulders falling on top of him.  Although he doesn't suffer quantifiable damage he has a very real sense of self preservation and finds getting 'hurt' very unpleasant indeed so avoids dangerous situations as if he were fully vulnerable.  This provides excellent roll playing opportunity as other characters are always trying to get him to test dodgy things out first but of course he doesn't want to.  He is affected normally by paralysis, poison and other physiological effects (like rooms full of green poison gas - DM.)

CHARACTER CLASS
Frilli is a Mage/Thief.  Strictly he shouldn't be multi-class as he is most definitely not a demihuman but Dave was happy to allow it once we had discussed how I envisaged the character.  Fremlins are inclined towards being Rogues as they are naturally mischievous and, rather like Dragonlance Kender, I see Frilli as having a very open policy on property ownership.  Frilli is not actively dishonest and tends to use his thieving abilities mostly either for self-preservation or playing practical jokes.

Frilli started as 5th level as Dave wanted the party to have a certain level of ability from the start to cope with the challenges of his campaign.  Frilli is now 6th level in both Mage and Thief and rapidly approaching 7th.

I haven't had much practice playing mages before as I find getting my head round all the technical spell stuff rather tedious, also mages always tend to be weak and vulnerable at lower levels.  I liked the idea of using magic but in a hap-hazard way with a harmless looking little creature that most enemies would simply overlook.  Frilli's size, dexterity and natural immunity to harm means he can either avoid or shrug off most damage.   

Much of Frilli's amusement value is due to his unstinting ineptness when casting spells.   Every time he casts a spell he must roll percentile dice against his adjusted 'Chance to Learn Spell' stat.  77% is pretty good odds but I still manage to fluff the roll more often than not.  If he rolls under, the spell is cast as intended but when he doesn't, Dave the DM determines the result.  Frilli is in effect his very own self contained Wild Magic Region so Dave rolls percentiles against the Wild Surge Results table from the Tome of Magic and then combines it with a liberal dose of  mischief to determine the final effect & target.  He uses his discretion against disproportionate results thus avoiding the whole party being obliterated by a fireball when a simple cantrip goes wrong.

Frilli has the use of 20 spell points per day.  He can continue to cast spells, including multiples of the same spell, until he no longer has enough points left.  At this point he must rest up and 'regenerate' his magic potential.  Spells require a number of spell points to cast equal to their level - e.g. the 3rd level Fireball spell requires 3 spell points to cast.

We follow the rules for casting time but are pretty lax about spell components.  Provided Frilli has free arm/hand movement and is able to speak (and be heard) it is assumed that any verbal & somatic requirements are met.  As far as material components go it is assumed that any necessary items are at hand and are replenished when opportunity arises i.e. when in town.  We just can't be bothered keeping tabs on what component items mages have with them and how/when they are obtained - it's just too much hassle and detracts from the flow of the game.

When Frilli is faced by a particularly scary situation I volunteer to make a saving throw against Paralysation & Poison.  If he fails he is frozen with fear and loses his ability to function rationally.  At Dave's discretion he may cast spells but suffers a -19% penalty to his normal roll.