Not sure I have a favorite but the model T going around the white house was good. Also the villain, owner of the “auld lang sine” loan company bouncing higher and higher was funny.
That’s hilarious. Especially when the football team has to tackle him to get him to stop bouncing.
Sidenote: Keenan Wynn who played the villainous Alonzo Hawk not only revived his character for the 1963 sequel “Son of Flubber” but also for the 1974 Disney comedy “Herbie Rides Again”. So he got to battle both Flubber and the Love Bug!