How many movies have Mona Fong Yat-Wah and To Siu-Ming collaborated on?

They have worked on 10 movies together! Their first movie together was Hex vs. Witchcraft (1980) while their highest rated movie together was Hong Kong Playboys (1983). They have not worked together since Wits of the Brats (1984). They are most known for their comedy films together.