On the September 22, 2023 episode of SmackDown, Austin Theory and Grayson Waller teamed up to defeat The Brawling Brutes (Butch and Ridge Holland) in a match. On the October 13 episode of SmackDown, Theory and Waller challenged Cody Rhodes and Jey Uso for the Undisputed WWE Tag Team Championship in a losing effort. On the November 10 episode of SmackDown, Waller and Theory provoked the newest member of the SmackDown roster Kevin Owens, resulting in Owens attacking both of them and being suspended by WWE. On the December 15 episode of SmackDown, both Waller and Theory lost in the first rounds of the United States Championship number one contender's tournament to Carmelo Hayes and Owens respectively.
On the January 12, 2024 episode of SmackDown, Theory faced Hayes, but their match ended in a no contest after both of them landed on their heads from the top rope. Theory proceeded to defeat Hayes in their rematch on the January 26 episode of SmackDown after interference from Waller.
On February 24, at Elimination Chamber: Perth, Theory and Waller co-hosted The Grayson Waller Effect featuring Cody Rhodes and World Heavyweight Champion Seth Rollins. After imitating The Rock, Rhodes and Rollins attacked Theory while Waller did not get involved, teasing the dissolution of A-Town Down Under. Nevertheless, Theory and Waller entered a tag team tournament, defeating The O.C. (Karl Anderson and Luke Gallows) on the March 22 episode of SmackDown and The Street Profits (Angelo Dawkins and Montez Ford) in the finals a week later to qualify for the six-pack ladder match for the Undisputed WWE Tag Team Championships at WrestleMania XL. On night one of WrestleMania XL, Waller retrieved the SmackDown Tag Team Championships for A-Town Down Under to become the new champions, although they failed to win the Raw Tag Team Championships as they were won by The Awesome Truth (R-Truth and The Miz). On the April 19 episode of SmackDown, the SmackDown Tag Team Championships were renamed as the WWE Tag Team Championships and the team was presented with new title belts by Triple H and SmackDown General Manager Nick Aldis. On the May 3 episode of SmackDown, A-Town Down Under defeated The Street Profits in their first title defense. On the July 5 episode of SmackDown, A-Town Down Under lost the titles to #DIY (Johnny Gargano and Tommaso Ciampa), ending their reign at 90 days. They failed to win the titles in a rematch on the following episode of SmackDown, ending their feud.
On the September 6 episode of SmackDown, A-Town Down Under faced Kevin Owens in a two-on-one handicap match, but we're unsuccessful as Theory was pinned. After the match, Waller carried on the attack on Kevin Owens and the two double teamed Owens and then left. On the September 13 episode of SmackDown, Theory and Waller faced Owens and his mystery partner Randy Orton in a tag team match, but were unsuccessful.
Theory and Waller returned to NXT on September 24, challenging Fraxiom (Nathan Frazer and Axiom) for the NXT Tag Team Championships, which they accepted. Later that night, they defeated Cedric Alexander and Je'Von Evans following a backstage confrontation. On the October 8 episode of NXT, they failed to win the titles from Fraxiom.