Brock Lesnar made his WWE return after 504 days at the end of SummerSlam. His appearance stunned everyone, as did his new hair and beard, and many current and former WWE Superstars reacted to his shocking return on Twitter.Roman Reigns defeated John Cena to retain the Universal Championship in a stellar main event at SummerSlam. After the match, as The Tribal Chief was celebrating his victory, The Beast Incarnate's music hit to everybody's surprise.HE'S HERE. @BrockLesnar IS BACK! #SummerSlam pic.twitter.com/QgvrKbky7e— WWE (@WWE) August 22, 2021Lesnar showed up in a tank top and jeans, sporting a beard and ponytail, as fans at SummerSlam went completely wild. He stood face-to-face with Reigns. However, the Universal Champion would retreat out of the ring, living to fight another day.The eight-time WWE World Champion ended SummerSlam alone in the ring and proceeded to destroy a defeated Cena after the show went off the air. Twitter was a stunned place as this ordeal unfolded, yielding some great reactions.Fans and wrestlers shared their reactions to Brock Lesnar's stunning return to WWE, with some hilarious memes ensuing. Check them out:Ponytail @BrockLesnar is the shit— Renee Paquette (@ReneePaquette) August 22, 2021THE ALPHA MALE OF OUR SPECIES IS BACK#SummerSlam pic.twitter.com/DFvNgQX7PR— Pat McAfee (@PatMcAfeeShow) August 22, 2021to football? https://t.co/H5ld0XxBzr— Nic Nemeth (@HEELZiggler) August 22, 2021Yo @BrockLesnar better look JUST like this in #WWE2K22 #SummerSlam— Just Different (@swerveconfident) August 22, 2021The #SummerSlam Main Event was GREAT story telling@WWERomanReigns @JohnCena made people believe@BrockLesnar return was icing on the cakeAlso Brock if you need a NEW advocate to counter @HeymanHustleWe have matching ponytails#JustSayin@WWENetwork @peacockTV— Tommy Dreamer (@THETOMMYDREAMER) August 22, 2021There’s only one way to settle this feud between Roman Reigns and Brock Lesnar… pic.twitter.com/q1dCubfoLI— Kenny Majid - The Not-So-Jaded Member of the IWC (@akfytwrestling) August 22, 2021#SummerSlam pic.twitter.com/38vTjHHpcu— Adam Pacitti (@adampacitti) August 22, 2021POS— TeM̺̤͍͓̮̼̟̂ͯ̽͒͐̋ͧA͈͋C͕̥̘̬̊̇ͪ͂E̳̽ous D. (@MACEtheWRESTLER) August 22, 2021Brock looks like friggin Goro.— Tag Team Titles-BAR (@TBARRetribution) August 22, 2021Brock Lesnar hitting the F5 on John Cena after #SummerSlam went off the air!! pic.twitter.com/YPaxRaTwzk— Ryan Satin (@ryansatin) August 22, 2021Here we go everybody. Brock looks phenomenal #SummerSlam pic.twitter.com/sLetOjvCZC— David LaGreca (@davidlagreca1) August 22, 2021He’s back😈— Parker Boudreaux (@ParkerBoudreaux) August 22, 2021We currently have John Cena, Edge, Brock Lesnar & Rey Mysterio on the Smackdown rosterThe Ruthless Aggression Era vibes are too strong pic.twitter.com/sP3MDtMaQL— Wrestle Views (@TheWrestleViews) August 22, 2021Brock Lesnar was not the only surprise return at WWE SummerSlamWhile Brock Lesnar ended SummerSlam with his grand return to WWE, Becky Lynch came back in the middle of the card. She replaced Sasha Banks as Bianca Belair's opponent for the SmackDown Women's Championship at the event.The Man would win the title after a 26-second match, in which she pinned The EST of WWE with her own version of the Rock Bottom. This title change has garnered its own set of wild reactions on Twitter, which you can check out HERE.Both Lynch and Lesnar had last wrestled for WWE at WrestleMania 36 - the first pay-per-view without any fans. Fast forward to SummerSlam 2021, where the two of them made surprise returns in front of over 50,000 fans at the Allegiant Stadium in Las Vegas.Are you excited to see Brock Lesnar back in WWE? Let us know in the comments below.