Christopher Lee said:
My apologies if this has been posted before. I've never cared for the idea that Dooku was trained by anyone other than Yoda; the novels establish that his master was Thame Cerulean. Although Yoda participated in the training of many Jedi (as evidence by his teaching a group of Younglings), Attack of the Clones established that Dooku had been his Padawan. The mention of another master for Dooku seems redundant and unnecessary.
It is also implied in the OT that Obi-Wan was Yoda's padawan.