Aisling Bea and Sharon Horgan have been good friends ever since they played sisters on the BBC show Dead Boss (2012).
When casting the students for the classroom sequence in which English is being taught as a second language, creator Aisling Bea insisted on actual foreigners, opting for authentic accents as opposed to faked ones.
Pik Sen Lim, who plays the elderly Chinese student in the class, also played a Chinese English student (Chung Su-Lee) in 'Mind Your Language'.
The series was originally titled "Happy" but clashed with other similarly named shows.