1. John Lennon: English singer-songwriter, musician, and co-founder of The Beatles.
2. Yoko Ono: Japanese multimedia artist, musician, and peace activist, and Lennon's wife.
3. Paul McCartney: English singer-songwriter, musician, and co-founder of The Beatles.
4. Linda Eastman: American photographer and musician, and McCartney's future wife.
These four individuals were involved in the motorcycle accident that occurred on June 12, 1969, while they were on a trip to Scotland. The group was traveling on motorcycles when Lennon and Ono were involved in an accident, with Lennon sustaining a broken collarbone and Ono suffering minor injuries. McCartney and Eastman were not involved in the accident itself but were present at the time of the incident.