While writer Kevin Lehane was backpacking across the world and being bit by mosquitoes, he heard the urban legend that eating Marmite (a vitamin B rich yeast spread) prevents mosquito bites. Hearing that, he wondered whether mosquitoes also got hungover from drunk people's blood. The thought stayed with him until he returned home and wrote the script for Grabbers based on the premise 'get drunk to survive'.
Before shooting, director Jon Wright took actors Richard Coyle and Ruth Bradley out drinking and filmed them while drunk. Ruth Bradley discovered many quirks about herself while drunk that she used in her performance.
The film shot during the harshest winter in Ireland in over a hundred years. Uncharacteristic blizzards, gale force storms and sub-zero temperatures regularly hampered production, creating a difficult shoot.