Katy Perry kicked off her 'Californian Dreams' tour in Portugal on February 20th in Lisbon, Portugal, and made sure to wish her BFF Rihanna a Happy 23rd birthday.

Here's a video of miss Perry slowing things down in her show with a cover of Rihanna's "Only Girl In The World", Jay-Z "Big Pimpin'" and Willow Smith's "Whip My Hair". Check out her amazing flute skills too!

What do you think of her covers?