Bruno Mars and Katy Perry continue their game of explosive musical chairs as  “Grenade” blasts back up to No. 1 on the Billboard Hot 100 this week, replacing Perry’s “Firework.” This marks the third time the two have switched places.

(However, it looks like there will be a new girl in town next week as Britney Spears’ “Hold It Against Me” is likely to debut at No. 1, according to Billboard. )

[More after the jump...]

Mars and Perry aren’t the only flip-floppers: Rihanna’s “What’s My Name” (4-3) and Ke$ha trade spots this week too. Plus, Black Eyed Peas’ “The Time (Dirty Bit)” switches places with Wiz Khalifa’s “Black and Yellow” (7-8).

Pink’s “Raise Your Glass” stays at 5, Enrique Iglesias’s “Tonight (I’m Lovin’ You)” remains and 6 and Bruno Mars’ “Just The Way You Are” holds at 9. Rihanna’s “Only Girl in the World”  is No. 10, a jump of two spots.

The number of debuts remains slow as radio reawakens from the holidays.  Gwyneth Paltrow’s “Country Strong,” the title track to the movie, bows at. 81. The only other debut also belongs to a country artist, Sunny Sweeney,” whose “From a Table Away” comes in at No. 96. It is 16 on Top Country Songs.