I would say that secrets generally give you a reward, whereas Easter eggs are just there for fun! Here is pretty much every little reference and detail I could find in the entire game. Some are small, some might be a bit of a stretch, but they're all interesting!
Sections:
0:00 - Opening Screen
0:58 - Villagers and Stardrops
2:54 - Ghibli and game references
4:51 - Rare Occurrences
6:07 - Snooping Around
7:14 - Finally, a Use for Holly
8:36 - Painting References
10:16 - Out of Bounds Dialogue
11:01 - Clothing References and the River King
13:52 - The Doctor's Office and Salad Fingers
14:53 - Locations of Ferngill
15:58 - References to Stardew Valley
Here's the lofi Stardew Valley music I use a lot:
https://djcutman.bandcamp.com/album/stardew-chill
🕹️ Stream Archives: https://www.youtube.com/channel/UCfYxeuIkNALOBeSpVEI4ipQ
💜 Twitch - http://www.twitch.tv/salmence100
🍊 Patreon - https://www.patreon.com/salmence
🕶 Tik Tok - https://www.tiktok.com/@salmence?lang=en
🐦 Twitter - https://twitter.com/Salmence100