1993: Princess Sparkle
Pink earth pony coated in irridescent glitter, with lavender purple mane and tail threaded with irridescent tinsel. Yellow crown tiara with fibre-optic lights, pink removeable cape on back with crown motif and white edging (this is a battery case cover) and yellow collar with turnable yellow bow.
Hasbro really pushed the boat out this year with Princess Sparkle. I think to be quite honest even 'Sparkle' is something of an understatement, since there isn't a part of her which doesn't glitter, glimmer or glint in some way or another.
And if her gaudy outward appearance wasn't enough, Sparkle's yellow tiara crown also had a light up function. Batteries went under her pink cape and the colours of the tiara and the lightswitch on and off could be controlled by turning the bow on her yellow collar.
I know, right? :S
Princess Sparkle was only sold in Europe/the UK/Australasia and was the ultimate gimmick pony from 1993. She did make a brief appearance in one of the pony comic stories as far as I remember, as part of one of Sweetheart's dreams. Her backcard story had something to do with getting ready for a party to which the Seven Characters were invited. She was also sold with a glittering star pick like the ones sold with earlier Princess ponies.
She was also sold in great numbers at markdown prices at the end of the run - often in French or German boxes. Her name in French was Princesse De Lumiere and if I remember rightly, in German was Prinzessin Gloria.
She's not to be confused with the American name for Princess Amethyst, which is also 'Sparkle'.