Exactly a year after Rocko's Modern Life had ended, Stephen Hillenburg and several crew members of Rocko's Modern Life begun working on a pilot for Spongebob Squarepants. The original name for Spongebob was SpongeBoy and the show was to be called SpongeBoy Ahoy!
This idea was ultimately scrapped and replaced with Spongebob Squarepants due to a cleaning product of the same name existing. To avoid copyright infringement, it was reworked.
It is said to be a version of Help Wanted with a different intro sequence and Spongebob is known as Spongeboy.
Despite this, the original SpongeBob pilot has yet to surface online. The only evidence of its existence is the original opening sequence found and a rare screenshot that's very hard to come by of what appears to be the original Spongebob auditioning for a place at the Krusty Krab. Asides that, nothing else has found its way online or one home media.
It is currently unknown if Hillenburg himself or anyone else working on this Pilot still has a full copy.
EDIT 11/24/15: The SpongeBob version of this pilot has been uploaded by LMW user "Joey!" on Vimeo. https://vimeo.com/137892254 The password is AHOY. It's basically identical to the "Help Wanted" segment in the first official Spongebob episode, except some minor differences including the opening sequence.
EDIT 5/14/16: YouTuber Garfield Cat recorded the end credits of the Vimeo vid, and posted it on YouTube. It is blocked in some countries. You can watch the video here.
EDIT 6/11/16: Garfield Cat terminated his account, making it unwatchable.
EDIT 8/16/16: YouTuber and LWM user NormTendo64 found out in the Nickelodeon Animation 25 year anniversary video on The Splat's YouTube channel. He found a screenshot of the pilot. Here is the picture.