The "South Park" creators announced Friday they struck a deal to become the new owners of the Mexican restaurant made famous by their show, breaking the news in an interview with Colorado Gov. Jared Polis.

Bob Wheaton, the president of Casa Bonita's parent company, Summit Family Restaurant Inc., tells TMZ ... the deal was put together VERY quickly, with talks heating up Wednesday during a conference call with reps for Trey and Matt.

We're told Trey and Matt's team laid out a detailed plan for how they wanted to evolve the business, including pouring resources in to expand the food offerings, gift shop and arcade at Casa Bonita.

As we first told you ... Casa Bonita's corporate ownership was not interested in selling as recently as 2 weeks ago, despite filing for bankruptcy ... but Wheaton tells us Trey and Matt ultimately got Casa Bonita for 2 main reasons.

First, we're told Trey and Matt offered a "fair" price for Casa Bonita ... the exact price was not disclosed, but we're told the amount was one Summit would have sought in the future.

Second, we're told Trey and Matt also struck a deal with the restaurant's landlord, something corporate had been unable to do since March and an issue that lead to the bankruptcy filing.

Ultimately, we're told Casa Bonita is in good hands with its new owners ... and it sounds like everyone's happy.