life of the party

(idiomatic) A person who participates in entertainment events in a very enthusiastic manner and who has a leading role in inspiring others to join in the spirit of festivity.

Example: 1846, Charles Dickens, Dombey and Son, ch. 37,
  â€˜You were the life of the party last night, Ma'am, you know,’ returned Flowers, ‘and you suffer for it, to-day, you see.’
1915, Edward Stratemeyer, The Rover Boys in Business, ch. 30,
  Tom was the life of the party, and the way he "cut up" was "simply awful," as Nellie declared.