The Royal Rumble has a long history, with the event first being run in 1988. 31 years later and the tradition of the Royal Rumble appears to have been set. However, the match has seen changes in the rules from the number of entries to the gap between entries, and even to the rules of elimination, nothing appears to be set in stone when it comes to the Royal Rumble.
When the Royal Rumble first started in 1988, there was a 2-minute gap between entries for the 20 man Royal Rumble. The next year saw the participants increase to the now traditional 30. The gap between entries was shortened to 90 seconds, but this isn't kept to the second. The WWE also had a 40-man Royal Rumble in 2011, with entry 38, Alberto Del Rio coming out the winner then. They went back to the traditional 30-man format the next year and haven't strayed from that path.
The rules have also been flexible, with Andre the Giant eliminating himself from the 1989 Royal Rumble to put distance between himself and Jake the Snake Roberts' snake that he had thrown in the ring. However, when Randy Savage climbed the turnbuckle to hit an elbow drop on Jake Roberts, he was able to climb back into the ring leaving Gorilla Monsoon to clarify that Savage wasn't eliminated as he took himself out of the ring. The rules returned to normal by 1997, when Mexican luchador Mil Mascaras eliminated himself after climbing the turnbuckle to drop on to fellow Triple-A wrestlers Cibernetico and Pierroth.
You can see the other entries in this series below:
#5 Brock Lesnar (2017) - Eliminated 19th - 3 Eliminations
Brock Lesnar entered the 2017 Royal Rumble as a hot favorite, as he had previously won the Royal Rumble in 2003 during his first run in the company. With the winner of the Royal unclear, Lesnar had been dominant for the most part since once again returning to the WWE ring.
Lesnar entered the Royal Rumble and quickly eliminated Dean Ambrose, Dolph Ziggler, and Enzo Amore before coming against the only wrestler that had given Lesnar a run for his money, Goldberg. The former WCW legend, that had eliminated Brock Lesnar from the 2004 Royal Rumble, as well as having beaten Lesnar at Survivor Series in a squash match the previous year.
Lesnar was once again eliminated by Goldberg, who he would once again face at WrestleMania, this time coming away with the victory and getting his first reign as the WWE Universal Champion.