Regular Show (partially found Flash pilot of animated series; late 2000s-2010)
Regular Show was an animated show created by J.G. Quintel. Its first episode aired on Cartoon Network on September 6th, 2010, but before that, an 11-minute pilot was aired called "First Day". Before even that, however, two other pilots were made, one of them being Flash animated. The story of this pilot is not known, but it's likely similar to the final pilot.
The full Flash pilot hasn't been put online as of yet. However, two short clips of it are available. The first part is the intro of Mordecai and Rigby playing "punchies" for the bowl of cereal and the second part being the segment where they are about tying their game of rocks-papers-scissors 100 times. Both of these parts, as stated before, are just like the actual final pilot.