a) series order: this is often to allow a "cliff-hanger" to go over the split in two DVDs, to encourage us (like we needed it) to go and buy a second one... [this applies to the moving of "Spirits", to allow Tokra 1 & 2 to be split]
a2) some don't seem to have been moved for such a sensible reason: "1969" and "Show and Tell" are swapped, so that "1969" is now on a separate DVD from the preceding "One False Step". Yet as we all know there is a major (if small) factoid from the "One False Step" which was so small, and because of the gap waiting for the next DVD, I missed!!:blush: Perhaps it is because there is a (minor) link...?
b) DargonBaby - you are perhaps confusing Region 1 and Region 2 DVDs? It is a point made throughout this BBS that there is a total lack of sense when it comes to MGM releasing DVDs.
In the US, you can buy the whole of series 1 on Region 1, with the odd episode evailable singly. But none of series 2, 3, 4 or 5.
In the UK, you can buy the whole of series 2 and 3, and within a couple of months 4, in 4-episode chunks. [I guess series 5 will come available sometimes next year?] You can also buy PARTS of series 1, i.e. episode 1, 8, 13, 19, 20, 21; and these are split into DVD1, and then two episodes (8: Thor's Hammer and 13: Hathor) are squeezed onto the end of series 2!
They wasted the end of series 3 (and 4 from a thumbnail) because they only put two full episodes on it, although they add an hours (or less) documentary. They could have added more series 1 episodes into the "spare" slot, since ones such as "Singularity", "The Nox" and "Enigma" add important characters/races who reappear, often more than once.