Crossword Dictionary
lark
frolic, lark, rollick, skylark, disport, sport, cavort, gambol, frisk, romp, run around, lark about - v 
play boisterously; "The children frolicked in the garden"; "the gamboling lambs in the meadows"; "The toddlers romped in the playroom" 
A lighthearted, fun episode is a lark. You could describe the wonderful day you spent with friends exploring little fishing towns along the coast of Maine as a lark.
Often unplanned, a lark can happen when you are feeling adventurous. You might decide on a lark to audition for a reality show — and be picked! The act of trying something new like this can also be called larking.
etymology
"spree, frolic, merry adventure," 1811, slang, of uncertain origin. Possibly a shortening of skylark (1809), sailors' slang for "play rough in the rigging of a ship" (larks were proverbial for high-flying). Or perhaps it is an alteration of English dialectal or colloquial lake/laik "to play, frolic, make sport" (c. 1300, from Old Norse leika "to play," from PIE *leig- (3) "to leap") with unetymological -r- common in southern British dialect. The verb lake, considered characteristic of Northern English vocabulary, is the opposite of work but lacks the other meanings of play. As a verb, from 1813. Related: Larked; larking.