They were on the "Mickey Mouse Club" together:
Then he came on "The Voice" where they butted heads all season.
Here is a short timeline of events:
Justin Timberlake took to twitter in support of his friend:
Tony doesn't know why she is bitter:
But maybe it's because Christina was in love with Tony?
Former MMC member Dale Godboldo spoke to TMZ about the spat.
But today, Us Magazine reported that the two have let bygones be bygones:
"She just wanted to clear the air a bit," Lucca, 36, explained to Us Weekly of the private chat. The "Dirrrty" singer "apologize[d] that this became much more of a dramatic thing than she ever intended it."