Whether RuPaul would have achieved the same level of prominence without the help, support and friendship of Todrick Hall is unknown. There's no denying RuPaul's talent, but having a well-connected and supremely-talented friend in the business definitely helps. She has appeared on the show, but not as a contestant. She's too well-known and polished for that! She's served as a judge on many of the shows, and also works behind the scenes as a choreographer and a coach. Her 'tough love' style of coaching has occasionally been upsetting for the performers, but always leads to higher standards being achieved.
Despite being a big name within the drag community, Hall wasn't well-known with wider audiences until her first appearances on the show during the ninth season. She's an outstanding singer and dancer, having secured a role in 'Kinky Boots' as Lola, and then reproducing that performance to the delight of viewers and her peers on 'Drag Race' during a lip sync.