To "trip the light fantastic" is to dance nimbly or lightly to music. The origin of the phrase is attributed to John Milton.[1][2]
^Kirkpatrick, Betty and Kirkpatrick, Elizabeth McLaren (1999) "light fantastic" Clichés: Over 1500 Phrases Explored and Explained Macmillan, New York, page 115, ISBN978-0-312-19844-2