The Incredible Machine 2 was released by Sierra in 1994. It still uses 640x480 16-color VGA graphics, but this time the animation and effects are improved.
To make the game has a funnier and lighter feel, Professor Tim was introduced. Professor Tim is a cartoon character with quite some animation on him. It's kind of refreshing to see him in action.
The Incredible Machine 2 introduced new levels, an extended assortment of parts, a new interface, significantly improved graphics, sounds and music, and two player hotseat play.
It also improved on the "freeform" mode, allowing players to create completely playable puzzles by defining not only the participating parts, but also the set of circumstances under which the puzzle will be considered "solved".
In terms of gameplay, this version provided the biggest addition to the series, while subsequent updates were basically only ports of the game to newer operating systems with updated graphics/sounds and sometimes new puzzles, but no new parts.
You can get The Incredible Machine 2 here.