Fifth Harmony closed out 2014 with a bang and they've opened 2015 with a bang too.

Fifth Harmony Teases Fans On Twitter About Surprises Coming In 2015 & Fans Speculate

The girl group teased fans on New Year's Eve about what 2015 would bring for them.

Ally Brooke Hernandez, Normani Kordei Hamilton, Lauren Jauregui, Camila Cabello and Dinah Jane Hansen revealed fans should mark their calendars for Jan. 7 for the group's first surprise of 2015.

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On Jan. 1, Jauregui took to Twitter to share lyrics to Mark Ronson's song Uptown Funk featuring Bruno Mars.

Her tweet included a link to an Instagram post she made of her and her bandmates singing a snippet of the lyrics she tweeted. The short video clip shows the text, "#5HIN2015" and "COMING JANUARY 7TH 2015".

The group's Facebook page also posted the snippet.

Then on Friday, Cabello tweeted, teasing another snippet of the girls singing a segment of the song, but another voice was present in the short clip.

She asked, "hear any familiar voices?"

uptown funk you up, uptown funk you up........ hear any familiar voices? #5Hin2015 Um vídeo publicado por camila_cabello (@camila_cabello) em Jan 1, 2015 at 3:04 PST

Then singer, Jacob Whitesides, tweeted the 5H member asking, "who is that???," which led to the 5H Twitter account retweeting him and therefore confirming he's the mystery voice in the Uptown Funk cover that'll be releasing on Jan. 7.

Fans excitedly shared how they were feeling about the girls teaming up with Whitesides.

Twitter user, cupcabello, said the cover will be "freakin awesome".

Another user, royalmota, claimed they could no longer function after listening to the snippet Cabello shared.

Many fans like pacsunxespinosa were just overwhelmed and tweeted "OMG".