#6 Eugene
Soon after Lesnar left WWE in March 2004, Eugene made his way up to the main roster and was featured heavily on RAW for the next few months, including a main event caliber match against Triple H at SummerSlam 2004. He donned the gimmick of a special person who was happy to be wrestling alongside his favorite Superstars.
Around four years before he was promoted to the main roster, Eugene competed in a 6-Man Tag Team match at OVW, alongside Brock Lesnar and Big Show. The trio defeated Mr. Black, Rob Conway, and The Collector in what was Lesnar's third match in OVW.
#5 X-Pac
Days before making his first-ever main roster appearance, Brock Lesnar competed in a string of dark matches as well as live show bouts. On the March 10, 2002, edition of WWE Live, Lesnar teamed up with former D-X member X-Pac. The duo took on Crash Holly and Randy Orton and managed to score a win over them.
Both Lesnar and Orton would soon make their way to the main roster shows and go on to become the youngest WWE and World Champions respectively in the next two years.