1. Lee Child as a police officer in Jack Reacher: Never Go Back

Author Lee Child has made cameos in both adaptations of his action-packed thrillers. In Jack Reacher (based on One Shot) he played a member of airport security, while in Never Go Back he reappears as a police officer. Both characters see Child handing lead actor Tom Cruise his possessions - symbolic of the author handing over creative responsibility. Watch the making of Lee Child's cameo in Never Go Back here.
2. S.E. Hinton as a nurse in The Outsiders

3. Irvine Welsh as a drug dealer in Trainspotting

4. John Irving as a referee in The World According to Garp
5. Kathryn Stockett on a church pew in The Help

6. John le Carré as a restaurant diner in The Night Manager