A song challenge is one of the features found in My Lips and the only online gameplay the series offer.
If players wish to send a challenge, they must simply go to My Lips, choose a friend and instantly send a challenge by selecting an appropiate song. Note that if the second player does not have the appropiate song (i.e. he or she has not bought it in the Lips Music Store), then the challenge will be rendered useless.
After the second player has successfully acepted a song challenge, each player will have two chances to be on top. A common tactic to speed up the process if you think you are going to win is to simply forfeit your second chance by selecting "End Song" instead of singing again. After both players have sung two times each, the winner is decided.
Song challenges are fully compatible between Lips titles, meaning one player can send a song challenge in Lips to another player who is playing Number One Hits. The latter introduces some enhancements to the song challenge interface, mainly the Avatar integration.
Players who successfully win challenges will be rewarded with achievements as well as 2 Avatar Awards, the Crystal Corduroys and the Crystal Mini (NOH and later titles only). A minor achievement is unlocked the first time a player wins a song challenge, while another is unlocked once a player wins 20 rounds.