A little while ago I hatched a Pichu from breeding my Raichu with a Ditto without a problem. Im not sure why but I tried to breed an Azurill by placing two Marill's, two Azumarill's and one of each with a Ditto in the day care at different times and all of them came out as a Marill. Can someone please tell me what's going on here?
Certain baby Pokemon require an item to be held. For Azurill you need to give the Marill/Azumarill a Sea Incense, then breed with a Marill/Azumarill/Ditto and you will get an Azurill.
See the bottom of our breeding page for a full list of Pokemon that need items.