According to The Hollywood Reporter, in what will be her first major feature role, the Australia-born Whelan will play Leigh, who tempts Owen Wilson's wandering husband after he's given a "free pass" by his wife. Waters will play Wannabe, a barista/DJ who becomes an obstacle to the pairing.
Jason Sudeikis, Jenna Fischer, Stephen Merchant and J.B. Smoove also star in the comedy, which started shooting Tuesday in Atlanta.
The Farrellys are directing the script they co-wrote with Pete Jones and Kevin Barnett and are producing with their Conundrum Entertainment partner Bradley Thomas.
No production date has been set.