1992:

SWEET TALKING PONIES

As the name of this set suggests, for the first time in 1992 we were introduced to two ponies who were able to talk back. In the North American issue, these ponies did not apparently have official names. In the UK, they were called Chatterbox and Talk-a-lot. To begin with, there was some amount of confusion about which was which, but the pink one is Chatterbox and the purple, Talk a Lot. The image below is from the UK box confirming the pink pony as Chatterbox, which was also supported by her more frequent comic appearances.

In the UK pony comic, Chatterbox and Talk a Lot were represented rather in the light of flappy ponies who rarely shut up and who sometimes caused problems with that fact. The ponies themselves, however, could only say three phrases apiece. In the English release, the ponies say the following:
"I'm Pretty"
"Comb My Hair!"
"I Love You!"
The speech was activated by pressing the pony's symbol.

Very deep, meaningful, conversational stimuli...but I suppose, more than most ponies could generally manage on their own. ;)

There were foreign language versions of these, too. I imagine that more exist, but in the Spanish release, the ponies said:
Vamos a Jugar (Let's go play)
Peiname (Comb my hair)
Dame un besito (give me a little kiss).
The Spanish Sweet Talking Ponies were called Mimoso (pink) and Charlatan (purple).

And in the German release, they only had two phrases:
"Ich Hab Dich Lieb" (I love you)
"Kommst Du Mein Haar?" (Will you comb my hair?)
I believe the German Sweet Talking Ponies were called Goldstimmchen (pink) and Goldkehlchen (purple).

You can download a clip of to hear each pony release talking by clicking on the language link:)

The UK release of these ponies had the same English voice as those sold in North America, so had an American accent.

SWEET TALKING PONY PROTOTYPE CHATTERBOX
UK INSERT 1991-2

There are some prototype insert images of this set with closed mouths, but the actual sold ponies had open mouths. Their poses matched some of the Pocket Friends Ponies. On one UK insert, only Chatterbox is shown, but both ponies were sold in the UK. They were also initially marketed just as "Talking Ponies", but when it came to release, they were labelled "Sweet Talking Ponies" on the package.In the UK they were sold in bordered boxes, as per the style for the year, whereas in the North American release I believe they were sold on card.

The My Little Pony comic in the UK ran a promotional competition to win a Sweet Talking Pony, in 1991, in which their names were stated clearly.