Okay, like Ninja said, every 256 steps there is a chance that the egg is going to be produced. If they have.....
Same species with different ID numbers:
Chance of getting an egg; 70% | Statement; "The two seem to get along very well!"
Same species with same ID numbers:
Chance of getting an egg; 50% | Statement; "The two seem to get along"
Different species with different ID numbers:
Chance of getting an egg; 50% | Statement; "The two seem to get along"
Different species with same ID numbers:
Chance of getting an egg; 20% | Statement; "The two don't seem to like each other"
Different Egg Groups:
Chance of getting an egg; 0% | Statement; "The two prefer to play with other Pokémon more than with each other."
No, the daycare man does not change what he says because of what I listed above. Pretty much all of your questions are answered by the info above.
Btw,I got this from Serebii