Bye-bye Big 12, hello SEC. Texas and Oklahoma are finally making their long-awaited conference switch.But first, it’s time to party with Bevo (the longhorn) and Pitbull (the human).The three-years-in-the-making switch to the Southeastern Conference for two programs that were co-founders of the Big 12 in 1996 officially happens Monday.And for their move to a league where “It Just Means More,” Texas and Oklahoma have scheduled big campus celebrations Sunday and Monday with carnivals, live music and fireworks. Oklahoma’s even stretches to events statewide.The SEC Network planned live programming from both campuses over the two days, and Longhorns and Sooners fans had their first chance to buy SEC-branded school merchandise.“This is a day we have been building toward for years,” Texas athletic director Chris Del Conte said.It’s a moment college sports in general has been building toward in the era of major realignment. The Texas and Oklahoma break from the Big 12 helped trigger myriad conference shifts with more on the way. By the first kickoff of the 2024 season, 11 so-called Power 4 programs will be in new conferences.The Big Ten will grow to 18 teams with USC, UCLA, Oregon and Washington poached from the Pac-12. The beleaguered West Coast league also lost Arizona, Colorado, Utah and Arizona State to the Big 12, and California and Stanford to the Atlantic Coast Conference. SMU leaps from the American Athletic Conference to the ACC on Monday as well.As for Oklahoma and Texas, they originally planned to join the SEC in 2025, but ultimately reached a financial deal with the Big 12 for an early exit. And they leave with a whole lot of hardware.Between them, the Sooners (14) and Longhorns (four) won 18 Big 12 football titles in 25 years, with Texas winning the crown last season for the first time since 2009.In its final year in the league, Texas won 15 league regular season or tournament championships across all sports, and national titles in volleyball and rowing. Oklahoma capped its final season with its dominant softball program winning its fourth consecutive national title in May. The Sooners beat Texas in the final.“Texas brings more tradition, more talent, more passion and more fight,” to the SEC, the school said on its athletics website.All that winning will be much more difficult to duplicate in the SEC. Oklahoma opens its first SEC football schedule at home against Tennessee on Sept. 21. The Longhorns debut at Mississippi State on Sept. 28.Since the start of the College Football Playoff in 2014, SEC schools have won the championship six times.Texas (2005) and Oklahoma (2000) were the only two schools to win national titles in football while in the Big 12.Some traditional rivalries will be stitched back together, and some torn apart.The Texas-Texas A&M rivalry is reborn. It had been on hiatus since A&M left the Big 12 for the SEC in 2012. Oklahoma’s Bedlam rivalry with Oklahoma State is ruptured.Texas spiced things up with Texas A&M last week when it poached Aggies baseball coach Jim Schlossnagle to Austin. At his introductory news conference, Schlossnagle warned Longhorns fans that the SEC is the “major leagues” of college baseball. The league has won the past five national championships.Texas and Oklahoma planned for thousands of fans to join their celebrations.Texas set up a central campus carnival. Fans will get autograph sessions with team coaches, and a chance to pose with the Bevo longhorn mascot for photos in the afternoon.Sunday night includes a scheduled concert by “Mr. Worldwide” pop star Pitbull on a stage underneath the campus’ iconic clock tower.Oklahoma’s celebration started Sunday night with a “Race to the SEC” 5k race through the heart of campus, with midnight sales of SEC merchandise and fireworks.Monday morning, former Sooners coach Barry Switzer will co-host a celebration breakfast in Tulsa and Oklahoma will host a campus party at the football stadium with live music and entertainment.“We couldn’t be more excited to join the SEC. Our teams are poised for success and look forward to the competition with many of America’s most outstanding universities,” Oklahoma athletic director Joe Castiglione said.