Video: "Kyrg-aoke" in session! Kyrgios and Kokkinakis perform Backstreet Boys hit at ATP Finals

The "Special K's", a fan-given moniker for the team of Nick Kyrgios and Thanasi Kokkinakis are known for their levity, and the pair were at it again at the ATP Finals.

The Australian duo were walking through the players tunnel as they headed out to the court for their debut match at the year-ending event. Along the way, Kyrgios broke out in song, belting the lyrics to "I Want It That Way", a famous hit from the pop group Backstreet Boys.

Perhaps inspired by his teammate, Kokkinakis joined Kyrgios as both men joyfully recited the lyrics as they walked through the tunnel, before breaking out in laughter soon afterwards.

Kyrgios and Kokkinakis captured the doubles title at this year's Australian Open, which enabled them to qualify for the ATP Finals. However, the Aussie duo have lost their opening doubles match at the elite event, before coming back from a set down to win their second doubles match on Wednesday.