A few thing straightened out...
I'll try to clear up the confusing mess that is the series' format, as people have asked questions about it here. It's two individuals serials (the first was just My Little Pony in 1984, the second Escape From Catrina in 1985). The style and cast changed somewhat between the two, and then again for My Little Pony: The Movie (1986). After this, the series began called 'My Little Pony and Friends', which combines a 'My Little Pony' segment with a totally unrelated one - Potato Head Kids, Moondreamers, or Glo Friends. This ran for *two* seasons, one of 50 episodes in 1986 (including a two-part repeat of the first special renamed 'Rescue From Midnight Castle') one of just 15 in 1987 (including a two-part repeat of Escape From Katrina).
There is no third season. There was a *completely different show* made in 1992 called My Little Pony Tales. None of the cast, crew or chracters are the same as in 'My Little Pony 'n Friends', and even the storyline bears little resemblence, as the ponies are now pretty much human girls with four legs.
Just thought I'd direct y'all to the wikipedia article, which is currently a lot more thorough and accurate than the information here.
http://en.wikipedia.org/wiki/My_Little_Pony_%28TV_series%29