Hate to revive an old thread, but I have some to add.
Bring another leena to home cape howl. Conditions: kid must not be in your party and it must be after you visit guldove after overhearing glenn talking to the flower stall lady, and before you change into Lynx. You will witness a funny scene between her and serge.
Confirmed. This one's cute.
Bring another kid to another cape howl. Conditions: leena must not be in your party and it must be after you fight karsh, and before you infi trate viper manor. You will witness a scene where Kid asks Serge if you remember. If you answer yes, then Serge will tell her about the dream about kid getting killed by him and kid will respond.
Confirmed. Question: Can you still get this scene if Leena joined you? Anybody know?
Bring Zappa to see Karsh in home world to witness a scene and find out what happened. Conditions: Must be after turning into Lynx before fighting Miguel.
He's got it backwards. You can't bring Zappa to Home's Karsh because Home's Karsh is dead. What you can do is bring Another's Karsh to meet Home's Zappa and Zippa for a sad little scene.
Bring Guile to see Sneff in home world on the Zelbess to find the truth about his 'bad debt'. Conditions: Must be after turning into Lynx, before entering Sea of Eden.
How can you have Guile in your party after becoming Lynx...? Answer: You can't! I don't know what he's talking about here.
Bring Sprigg to the Fortune Teller after coming back to learn more about her mysterious past. Condition: Must be after turning into Lynx.
Confirmed, but you don't learn very much.
Bring Greco to the Shop Owner outside of the Shrine in Another world to find out more of his mysterious past and learn what caused Ghetz's death. Condition: Must RECRUIT Greco while you are Lynx.
He totally doesn't know what he's talking about here. You can get the scene while you're Serge. Just put Greco in your group and talk to the shop owner. You MAY have to do this right after Greco joins you, but I'm not sure. Besides, I'm pretty sure you can't recruit any of Serge's friends while you're Lynx anyway, except for Pip.
Bring Harle to see Sprigg and find some funny sequence. Condition: Must have recruited both and have gotten Harle back by the Chrono Cross.
Nothing happened when I tried to do this. Perhaps I missed the window of opportunity.
Bring Korcha to 'element trader' in Another World to see a funny scene where Korcha tells the Mermaid to escape. Go back a second time to witness the Mermaid has escaped her tank and fled the city! Condition: Must have recruited Korcha and have Serge's body back after Terra Tower appears.
Confirmed.
Bring Norris to people in Termina during Porre Takeover. Condition: Must have Norris and Serge's body back.
Confirmed, but not much happens with this. I wouldn't call it a secret scene or anything.
Bring Glenn with Karsh to Isle of Damned to learn what his brother did. Condition: Must have recruited Glenn and have not fought Dario.
Confirmed.
Bring Glenn to fight with Dario and learn what happened to his brother. Conditions: Must have recruited Glenn and gotten Serge's body back.
Confirmed.
Bring Marcy before Fargo on home Zelbess to find a hint of why she is his daughter. Condition: Marbule must have not been saved and the concert already over.
Confirmed.
Bring Korcha to girl in Termina after Porre Invasion to see a rejection. Condition: Must be after Terra Tower appears and have recruited Korcha.
Confirmed.
Bring GrobyC before Norris in Home to find a tidbit of who he is. Condition: Must be after Porre Takeover and before rebuilding Viper Manor.
Confirmed, but you don't learn too much. If you're hoping for Norris to explain that Grobyc is Luccia's brother or something, forget it.
Here's a few more.
Talk to Mary (the sick little girl) in Another's Termina without Korcha in the party to learn that Korcha in fact has no father. And here I thought that Orcha was his dad.
I think you see some funny scenes if you take Miki to the old man at Belcha's place in Arni (Home), and Nikki to the old woman at Belcha's place in Arni (Another).
Luccia and Starky both react with amazement if they are in the lead of the party when you inspect the Neo-Epoch under Viper Manor, and even delve into some theorizing about the nature of the craft. Everyone else just asks something like, "Is this some type of transport?"
I know there are more. I'm replaying the game myself right now. I can add ones that I find.
OdF