Near the beginning of JOD's, NiGHTS is first introduced to Will by idly playing their signature "invisible flute". The melody they're playing? "Dreams Dreams", naturally.
In Journey of Dreams, NiGHTS very adamant that they didn't care what happened to themselves, as long as Wizeman was defeated, and everyone they cared about was safe.
At the end of Helen's story in Journey of Dreams, she runs to the concert hall where her mother is waiting worriedly. When Helen arrives mother and daughter exchange a smile. Then Helen takes out her hairband and lets her hair down and the pair preform beautifully.
After the performance (in the perfect ending) Helen takes her mother aside at an empty outdoor concert hall and does a private performance for her. But for some reason the lights go out. Helen at first screams and closes her eyes, but once she works up the nerve to open them again she sees Will, holding out a hand and smiling reassuringly. It then starts to snow and the pair share a laugh.
A meta example, the little Nightopians have gone from Ugly Cute coneheaded migets, to actually being cute.
Just about every version of the "Dreams Dreams" song counts.