Justin Timberlake fans got a little more than they bargained for at one of his recent gigs when he decided to change the words to a couple of songs.The pop star launched into the chorus of Amy Winehouse's track Rehab during a set in Zurich and appeared to use the song to take a cheeky pop at his former girlfriend, Britney Spears, singing: "Tried to make her go to rehab."And just in case his fans didn't quite catch the drift he also changed the words on the Gnarls Barkley hit Crazy.Of course it's not the first time the US heart-throb has sung about Britney as it was claimed he wrote Cry Me A River about his former love.The stars, who were Mouseketeers together when they were kids, looked as if they'd put the past behind them when Justin visited Brit during her stint at the Promises clinic in Malibu earlier this year.There was even talk of him helping her with her comeback. The pop princess is currently performing 15 minute gigs at House of Blues venues across America.But after hearing all this, JT may not even be on Britney's Christmas card list let alone her new album.© Independent Television News Limited 2007. All rights reserved.