What is the theme of this crossword?

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Across
  1. 1. Distilled spirit aged in barrels
  2. 4. Shakespeare’s tragic heroine
  3. 5. Metric prefix meaning one thousand
  4. 8. Informal word for father
  5. 10. Common nickname for Michael
  6. 12. Ballroom dance with slow-slow-quick-quick rhythm
  7. 15. Standardised clothing
  8. 16. Eleventh month of the year
  9. 17. Nickname for an American
  10. 18. A River mouth landform
  11. 21. Mountain range; also Spanish for “saw”
  12. 25. Academy Award nickname
  13. 26. Shouted follwing a great performance
Down
  1. 2. Place to stay while travelling
  2. 3. Largest ethnic group in South Africa
  3. 6. Country home to the Taj Mahal
  4. 7. Nickname for someone named Charles
  5. 9. The winner of a contest
  6. 11. Sport played with clubs and a small ball
  7. 13. Dramatic Argentine dance
  8. 14. French-speaking Canadian province
  9. 19. Italian car brand, ___ Romeo
  10. 20. Capital city of Peru
  11. 22. Shakespeare’s famous lover
  12. 23. Sound that bounces back
  13. 24. Imaging used to see bones