Johnson was joking about her history of dating musicians when the “Cruel Summer” singer suddenly joined her Saturday night. Pop music icon Taylor Swift made a surprise appearance on “Saturday Night Live,” joining her friend and the episode’s host, Dakota Johnson, for some laughs. Key points and original sources are listed below.

• Johnson was joking about her history of dating musicians when the “Cruel Summer” singer suddenly joined her Saturday night.S1

• Pop music icon Taylor Swift made a surprise appearance on “Saturday Night Live,” joining her friend and the episode’s host, Dakota Johnson, for some laughs.S2

• Taylor Swift gave Dakota Johnson some pretty sweet payback for appearing in her “Patient Zero” music video: the mega-star joined the Verity actress during her opening monologue tonight on Saturday Night Live. Perhaps it was just a birthday present for Johnson,...S3