The former IWGP Heavyweight Champion entered the WWE World Heavyweight Championship Royal Rumble match at #3, after #1 entrant and defending champion Roman Reigns eliminated #2 entrant Rusev.
This isn't the first time Styles set foot in a WWE ring. He had his first WWE (then WWF) match against The Hurricane in WWF Metal in January 26, 2002. When a WWE contract didn't materialize for him, he went to TNA and became its NWA and TNA World Heavyweight Champion on separate occasions. Then, he joined New Japan Pro Wrestling, became the leader of arguably the greatest wrestling faction today, the Bullet Club, and won the IWGP Heavyweight Championship.
Welcome "back" to the WWE, AJ Styles!
Rumble (non-)surprises
The "Roman Empire" had fallen; Reigns was the second to the last superstar eliminated in the rumble, and was therefore the former WWE World Heavyweight Champion. His official rumble time was recorded at 59:50 (longer than Jericho), even though he spent most of the time recuperating backstage after an ambush by the League of Nations.
Reigns' elimination came at the hands of the #30 entrant, WWE COO Triple H, who surprisingly (or unsurprisingly) came out of wrestling retirement after Reigns (kayfabe) sent him to the hospital after the events of WWE TLC. "The Game" became the third WWE Superstar to enter the Royal Rumble last and win the match, following The Undertaker (2007) and John Cena (2008).
And as per the stipulation set by Vince McMahon, Triple H is now a fourteen-time WWE World Heavyweight Champion and a guaranteed main-eventer at WrestleMania (unless booking plans change); The Authority holds all the cards once again.
WWE Divas Champion Charlotte also retained her title against Becky Lynch thanks to an assist by her father "The Nature Boy" Ric Flair, but her celebration would be cut short by Sasha Banks, who returns from injury, trapping the champion in her submission move The Bank Statement, seemingly teasing a face turn and staking a claim on the butterfly-emblazoned title.
Final thoughts
Speaking of "underutilized", fans have been clamoring for Daniel Bryan to make his comeback in the rumble, but that didn't happen. Bryan himself had been wanting to return; his doctors had medically cleared him, but the WWE doctors refuse to do so. I think it's only a matter of time before he decides to leave WWE and wrestle somewhere else if his pleas to return still keeps getting ignored.
The rumble was hyped as "One Versus All", but it seemed that Reigns' only opponents in the entire match was the League of Nations and The Authority. The creative team probably thought the assault on Reigns ending in him being brought to the back made him look strong when he returned to the match later on, but that in my opinion only served to make him look pathetic compared to when he finally snapped after getting screwed at TLC. Now that "The Big Dog" is title-less once again, one will have to wonder what desperate measures the creative team will take to make fans get behind Reigns once again, especially when he got booed at the rumble for the second straight year.
Also, WWE seemingly planted the seeds of a WrestleMania feud between Wyatt and Lesnar at the pre-Royal-Rumble episode of Monday Night Raw, and the events that transpired at the rumble match itself obviously watered those seeds. Surely, after what transpired at "the Orlando Screwjob", the fans would want to see the esteemed "Mayor of Suplex City" avenge himself.
Speaking of the Wyatts, Strowman is being groomed to be the WWE's new monster, as was evident when he eliminated the resident big men Kane, Big Show and Mark Henry. The latter three are nearing retirement age, and the WWE needs more big men to take the spots that they'll leave open; Ryback isn't anywhere close to any of the spots.
And then, finally, there's AJ Styles. He is currently WWE's biggest free agent acquisition--an internationally-renowned talent, at that-- and they'd do well not to put him in midcard status in future episodes of Raw or SmackDown. They better treat Shinsuke Nakamura, Karl Anderson and Doc Gallows good as well, if they indeed go to the E.
There is still one more pay-per-view before WrestleMania, WWE Fastlane, and it's surely going to be one heck of a road--a fast lane--to "the Grandest Stage of Them All".