Andrew Walker Recalls Filming 'Intense' Episode of “ER” with Rachel Boston Ahead of Their Reunion in Hallmark's “Birding” (Exclusive)

Some cycles are meant to beryllium repeated. That surely seems to beryllium nan lawsuit for Hallmark Channel favorites Andrew Walker and Rachel Boston.

The actors first appeared together successful an section of ER successful January 2008. Years later, they costarred successful Lifetime's A Christmas successful Tennessee. And, now, they're backmost together yet again for Hallmark Channel's Adventures successful Love & Birding, premiering Saturday, Sept. 27.

"Rachel does everything pinch specified an unfastened heart," Walker tells PEOPLE. "I for illustration moving pinch caller people, but to person personification who I person this history pinch was an astonishing opportunity."

Looking backmost connected his ER experience, Walker, 46, notes that nan section (called "Status Quo," which aired during nan deed NBC drama's 14th season) was "extremely intense."

"We played 2 subject people, and she gets backmost from Afghanistan, and she's pregnant, and it's not our baby," he recalls. "It's an section that talks astir rape successful nan military. We had to spell to a batch of different places emotionally."

Walker says it was shaper John Wells — who's besides worked connected specified different hits arsenic Shameless, The West Wing and, astir recently, The Pitt — who thought to brace him pinch Boston.

"He was nan 1 that said, 'Hey, you two, do a chemistry publication together because I consciousness for illustration there's chemistry here.' So, retired of each nan actors that had auditioned for that episode, he put america together and past ended up casting america successful those roles," Walker remembers.

Seventeen years later, Walker and Boston's latest collaboration, Adventures successful Love & Birding, is decidedly lighter fare.

“I americium truthful grateful to beryllium capable to show nan analyzable and beautiful communicative connected ER, but I’m besides truthful happy that [Adventures successful Love & Birding] is simply a lighter, happier story," Boston, 43, told EntertainmentNow. "We’re virtually retired successful nan woods, successful nature, and it was conscionable awesome knowing [Walker] truthful good that we could conscionable thin successful from time one.”

The movie, inspired by Sarah T. Dubbs' novel Birding pinch Benefits, follows a azygous mom (Boston) who agrees to beryllium nan partner of a vertebrate enthusiast (Walker) for a birding title but, owed to a miscommunication pinch a communal friend, thinks she's expected to airs arsenic his caller woman alternatively of conscionable his teammate. Needless to say, sparks, for illustration nan birds themselves, fly.

"It's a beautiful emotion communicative and a very absorbing 1 wherever we person this information nett of being capable to research pinch nan knowing that we're successful a caller relationship, erstwhile we're really not, we've conscionable really taken to each other," says Walker. "It's a beautiful movie astir patience and understanding."

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Adventures successful Love & Birding premieres Saturday, Sept. 27 astatine 8 p.m. ET/PT connected Hallmark Channel.