Welcome back to Billboard's weekly video show "Real-Time Rewind," which recaps the past week's hottest action on the new Billboard Real-Time Twitter Charts --Trending 140 and Emerging Artists -- and the news that's driving the action. Joe Levy is back in the studio on Episode 21, which features Taylor Swift, Gwen Stefani, and a special shoutout from Pete Wentz of Fall Out Boy.

VIEW THE REAL-TIME CHARTS: TRENDING 140 | EMERGING ARTISTS

So what was happening on the Real-Time Charts this week?

Taylor Swift continues the march towards the October 27 release of 1989, putting out another new song "Welcome To New York" on Monday, Oct. 20, which becomes Swift's fourth consecutive Billboard Twitter Trending 140 No. 1.

The Voice coach and No Doubt lead singer Gwen Stefani releases her first single, "Baby Don't Lie," off her upcoming album slated for an Oct. 20 release. It immediately shot to No. 1. "Don't Lie" -- Stefani's first solo release since 2006 -- held the No. 1 spot for 10 hours thanks in part to a Twitter Q&A she hosted after The Voice aired that night.

Fall Out Boy's new single "Centuries" hit the No. 1 spot when it was released in early Sept. This week, it comes back to the top after the release of its Gladiator-style official music video.

We're celebrating Halloween next week on Real-Time Rewind so make sure to visit Billboard.com to vote for Joe Levy’s costume!

The Trending 140 chart measures the acceleration of conversation around artists and their music, while the Emerging Artists chart measures the volume of tweets around new artists and their songs.