Pre purchase tickets from the machines in Lawsons Convenience Stores is the only way in Tokyo to get an entry ticket into Ghibli Museum. The museum is a wonderous place full of colour, movement, magic and fun. A must to do in Tokyo. Plus, the entry ticket is 3 stills from a Miyazaki movies!
This is the museum for Hayao Miyazaki's work. There are cat bus from Totoro, and the robot from the Castle in the sky. You have to buy the ticket with reserved time, on the day you go. You cannot buy the ticket at the window. I think tickets are sold at Lawson convenience store.