It sounds like a hilarious pitch for a road movie: Britney Spears and Mel Gibson head to Central America. High jinks ensue. But it turns out that random, what-the-heck premise is actually a reality. "Entertainment Tonight" reports the improbable pals are vacationing together in Costa Rica.

Seems Mel invited the unsafe-at-any-speed cautionary tale and her decision-making dad Jamie to join him as guests at his Costa Rican home (he reportedly plunked down $25.8 million for a 400-acre ranch last year).

On Thursday morning, Brit and Papa Spears winged out of Los Angeles with the weathered Oscar winner and his wife, Robin, on a private plane for what's expected to be a short holiday.

"They're just going away for a few days to relax," an insider downplays to People.

Spears, who has spent the last few weeks being shuttled to the gym, the recording studio and the set of "How I Met Your Mother," was sans sons Sean Preston, 2, and Jayden, 20 months, who are presumably with dad Kevin Federline. "ET" says they're not allowed to leave the country without "special approval."

You'll recall that Britney and Mel, who were once neighbors in a rarefied Malibu enclave, were last spotted together in March, when they broke bread at a Russian restaurant in L.A. a few weeks after she checked out of the psych ward. It was believed to be one of a series of meetings between the two.

"Mel and his wife Robin clearly saw a woman in crisis and wanted to extend themselves in any way possible," an insider told People at the time. "There are no expectations, there is no agenda. It's simply an act of human kindness -- one neighbor reaching out to the other."

Gibson, who is no stranger to a public backlash caused by bad behavior (see his 2006 DUI bust), also apparently offered Spears the wisdom of his experience.

"He understands what she's going through," a source told OK!. "And he certainly has advice on how to not let it destroy your life."