In the pilot, the character George Sunday was Jewish-English. He wasn't an Irish grocer until Ardal O'Hanlon asked for him to be. O'Hanlon wanted to best serve the script by doing an accent he was comfortable in.
The mouths of Finlay Stroud and Madeleine Mortimer who voice Ollie and Cassie are added on to the faces of the babies who play the characters, so that the talking looks more realistic.