What are those bumps on top of the Antonov-225?
According to the Airliners.net forum, they are fairings that cover hardpoints used for attaching outsize loads.


  Outsize loads that cannot fit into the capacious cabin (including Buran and Energiya components) are carried 'piggyback', the load supported on two main attachments above the center section. These supports and other smaller ones along the fuselage top are faired over when not in use.


The text is quoted from aeronautics.ru (web archive link).

Please note that the two large ones were not used for carrying the Buran space shuttle, as shown in the photo posted below. (More pictures here.)