I believe there is an oblique reference in Watching the Clock - Christopher has stated that he tried to reference every Trek episode involving time travel.Pretty sure ENT - "Twilight" has never been referenced.
EDIT: Yup. Page 121.
Well damn, that is pretty oblique. I didn't realize that was a reference.
Hm. Was "Tuvix" ever referenced afterwards?
The D'Arsay are referenced in a STO mission. In there, you have to scan their graves and find out the were pokliothermic, i.e. amphibian. That's why they revere the sun so much.
