Chimera

Kira letting Odo go. It's such a sweet moment, to see how much she loves him. And it's extremely telling that Laas so completely, utterly misses the point.

Since Odo links with Laas, and Odo carries the deadly anti-Founder virus at this point, it is certain that he infected Laas. The writers were aware of this point and considered bringing Laas back a few episodes later, showing signs of infection. In the end it was decided that there was no time to do this, and so Laas's fate is left uncertain.

In the spin-off novels, however, it is revealed that Laas made it to the Gamma Quadrant, joined the Great Link, as was cured.

A Chimera is a mythical creature composed of body parts from different animals, a reference to the Changeling's shapeshifting ability. Interestingly, the Chimera was killed by Bellerophon - and the next episode of Deep Space Nine would feature an Intrepid class ship called the USS Bellerophon.

The original ending had Odo transform into his liquid state, which Kira would snuggle into. The writers felt that this would look kind of icky, so they came up with the idea of having him transform into a cloud of energy. Oddly, this is something Odo has never demonstrated the ability to do before. One might suppose linking with Laas allowed him to learn some superior shapeshifting skills.