how were some of the effects done, like the flubber itself bouncing and such?
http://www.youtube.com/user/AuteurMotionPictures
I wondered that myself. Pretty cool basketball game. If it was me, I would have kissed one of the tall players on top of his head. Now that would have thrown them off!
shareSorry for the late reply ---
The numerous bouncing flubber balls in Prof. Brainard's garage were painted into each cel of the scene --- much like drawing a sequence of moving dots along the outer margin of a book, and then flipping the pages. You can see this by pausing the movie --- many of the balls are clearly drawn in. MacMurray would have had to pretend that there were flubber balls bouncing all around him, aided by cuts to Charlie reacting, or else responding to his trainer's cues.
Several of the flying sequences were process or matte shots, of a model car shot against, or along with a background.
The "flying" basketball players obviously had harnesses on them, and you can just occasionally make out the filament or fishing line used to make the "flubber-ionized" objects float in Prof. Brainard's garage.
But it has been reported that some of the scenes of the car taking off are still "closely guarded" Disney secrets !
"A bride without a head !"
"A wolf without a foot !"