Board Thread:The Reference Desk/@comment-15777163-20130824222917

I just finished watching Journey's End and somewhere in the episode when Donna becomes half Time Lord, the Doctor says that the Ood had predicted "The Doctor Donna". This is confusing me because i do not remember when or where the Ood had predicted this. I'm assuming that it was in the episode Planet of the Ood but i still don't know when they said anything about Donna becoming the Doctor. Someone please help me and clear this up for me. 