VIDEO: GREASE: LIVE's Vanessa Hudgens, Carlos PenaVega Sing 'Summer Nights' on 'Today'

"High School Musical" star Vanessa Hudgens and Carlos PenaVega, formerly of boy band Big Time Rush, are two of the stars of the upcoming live TV production of FOX's GREASE: LIVE. The actors stopped by NBC's TODAY to tell Hoda Kotb and guest co-host Jenna Bush Hager how much fun they're having despite the intensity of the rehearsals, and join in an impromptu sing-along of the show's classic number "Summer Nights." Watch the appearance below:

GREASE: LIVE airs Sunday, Jan. 31, 2016 7:00-10:00 PM ET live/PT tape-delayed on FOX! The show will reintroduce and reimagine some of the show's most memorable moments, great music and timeless love story to an entirely new generation. In this live television adaptation of the musical classic, the beginning of senior year means the end of Danny and Sandy's summer romance - until Sandy unexpectedly transfers to Danny's high school. With their friends pulling them in different directions, it's up to Danny and Sandy to stay hopelessly devoted as they make their way from Rydell High to a new frontier.

The live event stars Julianne Hough ("Safe Haven," "Rock of Ages") as the angelic "Sandy" - Rydell High's most talked-about newcomer - and Aaron Tveit ("Graceland," "Les Miserables") as bad boy "Danny Zuko." Also tapped to star are Vanessa Hudgens (Broadway's "Gigi," "Spring Breakers") as iconic bad girl "Rizzo"; Keke Palmer (SCREAM QUEENS, "Masters of Sex") as sassy Pink Lady "Marty Maraschino"; Carlos PenaVega ("Big Time Rush") as "Kenickie," Danny's tough-guy sidekick; multi-Platinum Grammy® Award-nominated singer and songwriter Carly Rae Jepsen as Pink Lady and beauty school dropout "Frenchy"; Kether Donohue ("You're The Worst") as Pink Lady "Jan"; David Del Rio ("Spare Parts," "The Troop") as T-Bird "Putzie; Jordan Fisher as "Doody"; and Andrew Call as "Sonny."