Ponies you renamed.

[Raindrop]

My sister and I had the G1 Bright Bouquet family as kids.  We renamed Daddy BB "Blueheart".  He was the only boy pony we had, so he had multiple wives!

[brightberry]

I think the only pony I renamed was "blue Ember".   The pamphlet I got called her Ember but she clearly was not.  I called her Blueberry and she was my favorite pony for a very long time.

[Crystal-Sushi]

I didn't intentionally but Baby Honululu became 'Baby Hula-Lula-Loo', presumably due to my unfamiliarity with Hawaii (I'm Australian lol) 

[Kitcatepic]

I had one of those fake g4 blind bag cake topper things and I thought is was an authentic blind bag pony at the time. the packaging said it was rarity when clearly it was not because it was a pegusus with a blue mane and a flower cutie mark. I ended up calling it lucket.

[CherryTreats]

I always called Baby Beachball "Baby Island Magic" because the one I bought at the store did not have a name on the card. On the back it said "Island Magic" so I assumed that must be her name. I was so surprised many years later when I found out that was not her name. She will always be "Baby Island Magic" to me though.

[VanillaBean]

I've always thought of So Soft Twilight as 'Candlelight,' as it irritates me that Hasbro recycled names within the same generation. Her symbol is so obvious too; I could never understand why they'd gone with Twilight again. If I owned any of the other G1s with duplicate names, I'd probably rename them too.
I never renamed any of my childhood G2s, as I was familiar with their characters from the magazines & PC game.

[kingluke]

I've always thought of So Soft Twilight as 'Candlelight,' as it irritates me that Hasbro recycled names within the same generation. Her symbol is so obvious too; I could never understand why they'd gone with Twilight again. If I owned any of the other G1s with duplicate names, I'd probably rename them too.
I never renamed any of my childhood G2s, as I was familiar with their characters from the magazines & PC game.

I also call her Candlelight. Her symbol matches better as you said

[freezestime]

The pony that kicked off my current MLP collection was a G3 Royalette found in a charity shop, and when I bought a complete Royalette I named the charity shop one Rescuelette.

[BlackCurtains]

I knew Baby Firefly, Racer and Rosedust's name but not Raincurl or Sunribbon. I think I called Raincurl simply Rainbow and Sunribbon Baby Rainbow