I'm not sure if this has ever been accounted for here, but I've just recently noticed these changes...I posted this on the Rarity Change Archives thread, too, but I'm not sure if it's ever frequently updated anymore, so:
Keeping an eye on my July 2008 pets, I've noticed that:
The Coontail became OMGsr
The Sunback became OMGsr
So did this pet
And the Non-Tag
And so did the Non-Moonswirl
If I just missed these sometime, let me know. Hope I was able to help out. Also, I'm not sure when this occurred for all of the pets but I've just recently (later this year) noticed the changes.