Quote Originally Posted by cmwinters
I heard a theory (for the life of me cannot remember where) that Tonks' original Patronus was a chameleon. Which I find quite amusing.

Remus had been off with Greyback's werewolves, spying for the Order, during the summer between OotP and HBP, and also while Tonks was on intermittent assignment at Hogwarts. Harry (and Professor Snape) saw her changed Patronus when Harry arrived at school.
The chameleon theory doesn't sound that bad, considering that Tonks is a Metamorphamgus. Though I don't see a chameleon as a powerful Patronus ...

We all know that Tonks likes Lupin. It's important to show her being concerned for him; especially at a time when the Second War is in full force (post-HBP of course).

I've seen a few Remus/Tonks fics set during HBP that are one-shots, and a bit hurried. Most of them are written from Tonks's point of view. Tonks's feelings should be explored in-depth without getting excessively sentimental (and OOC).