 The fourth track " Cool " chronicles Stefani 's previous relationship with Tony Kanal , featuring a new wave and synthpop production . The song was compared to Cyndi Lauper and Madonna songs from the 1980s . " Bubble Pop Electric " , the fifth track , is an electro song featuring André 3000 's alias Johnny Vulture . It tells of the two having sex at a drive @-@ in movie , and it was generally well received by critics , who drew comparisons to the 1978 film Grease and its 1982 sequel Grease 2 . " Luxurious " is a 1990s @-@ inspired R & B song that lyrically talks about the desire to be rich in love , simultaneously comparing Stefani 's lover with luxuries . The seventh track , " Harajuku Girls " , is a synthpop song that was described as a tribute to Tokyo 's street culture , produced by Jimmy Jam and Terry Lewis . 
