Well, they don't quite look like any snail eggs I've seen, which usually look like little round packets of clear jelly with dots inside, but it could be that they look like that and I just can't see the jelly part in the picture...
Going through process of elimination:
I can tell you almost certainly it's not the danios (they scatter theirs), or the platys (they're livebearers). Gouramis make bubble nests on the surface and place their eggs in it, so the only way the eggs could be theirs is if they've been building a nest (believe me, you would know), laid the eggs, and some fell out and somehow stuck to the leaf. So it's probably not them either. Corys DO lay eggs on things; sometimes it's glass, sometimes it's rocks or a leaf, but I have no idea what their eggs look like, having never seen any myself. I'm assuming the shrimp reproduce something like other crustaceans, and don't just leave eggs on things, so it's PROBABLY the snails. They are by far the most likely thing, they're always laying eggs. I'd say you'll know for sure when they hatch!
Hopefully someone else knows more than I do. I'm so curious, please post and let me know what was in the mystery eggs when you find out.
