Wow! I did not think that this game continues to live, wonderful news! I passed it twice 100% for 2 endings. There is a question to the author. I opened countless boxes and in one I got a new shocker. But I still didn't understand if there are secret scenes with him, except for dialogues, I would like a hint)
Wow, the shocker is VERY rare and i'm still working on getting that item myself, congratulations!
When you say "secret scenes with him" i think you mean Heracross? But no, I'm pretty sure if you've gotten the shocker you've probably seen all the scenes in the game... well, there are a few funny conversations if you pick funny dialog paths, or call certain pokemon on the phone, take pokemon into the back room.
It's no fun, but you might try taking Sandslash into Heracross's back room and just playing games with him and never having sex. Or calling Heracross on his own phone while he's in the shop! Little things like that ha ha. But no there are no big "Mew Under The Truck" types of secrets like a secret 12th pokemon or anything like that.