[Headie]

From Wikipedia

There are easter eggs to all previous Black Mirror episodes in this special, particularly during Joe's story.[10] During a UKN (The National Anthem) news report of the train crash, one of the lines on the news ticker reads “MP Liam Monroe claims Twitter account hacked” (The Waldo Moment). On the same ticker is the headline “Victoria Skillane appeal bid rejected”, which references the protagonist of White Bear and also appears in Greta's story. There are brief shots of "Hot Shot" (Fifteen Million Merits) and "Tonight For One Week Only" (The Waldo Moment) when Joe flicks through the TV channels. The pregnancy test Joe finds in the bin is the same type of test that Martha uses in Be Right Back. Bethany also sings "Anyone Who Knows What Love Is", the same song as Abi sings in Fifteen Million Merits. In the first story, one of the people watching Harry has the username I_AM_WALDO (The Waldo Moment).