1987:
Newborn Twin Ponies
The Newborn Twins were the new tinies on the block - younger, supposedly, than the Baby Ponies that up until 1987 had marked the bottom of the pony evolutionary ladder. Smaller than the Baby Ponies, with stumpy legs and cheeky faces, the first Newborn Ponies came in pairs - as Newborn "Twins". Though none of the Newborn Ponies ever resembled an existing adult pony in the way that Baby Ponies sometimes did, these twins had their own key features. In the first six alone were two sets of 'identical' twins - Milkweed and Tumbleweed and Rattles and Tattles - both of which were only distinguishable from each other by the pose used. And, as with other sets, there were unicorns, pegasi and baby earth ponies here too. Each twinset had a symbol unique to that pair - in some cases it was printed in the same colours and in others it was printed in reverse, but was similar enough to match the babies together. (The only exception to this rule were the Slumber Party Twins - see their page for more information)
There were six sets in total in the first release of Newborn Twins...but not all of them ever made it to the UK. The release here is a little bit confused. Though the Hasbro promotional catalogue for 1987 shows Jangles and Tangles alongside Sniffles and Snookums and Nibbles and Dibbles for UK release, when it came to the crunch it seems that only two pairs were issued after all.
THE HASBRO UK 1987 CATALOGUE: FEATURING JANGLES AND TANGLES
(scan courtesy of Pranceatron)
When the insert was printed, it only featured Nibbles and Dibbles and Sniffles and Snookums. Furthermore, only these two sets appeared in the Pony Comic or the Fact File, suggesting that somewhere late in production, Jangles and Tangles were dropped from the UK line.
1987 INSERT: NEWBORN TWINS (UK)
This is further confirmed by the UK release box for the twins, which only features the above two pairs. Both were introduced in the comic as enchanted drawings brought to life by Baby Lucky's magic. Both sets of twins had an identical box design release, with the stories for both twinsets featured on both release boxes (I have both and they are identical except for the names on the front xD). The insert art was clearly lifted from the box, something not uncommon in this year.
1987 Newborn Twins: UK release box
(click image for full size version)