A star in the making! Jessica Biel gave fans a look behind the curtain at what it's like to tour with Justin Timberlake, and it honestly looks like nobody's having more fun than their youngest son, Phineas! In the Instagram slideshow posted on Wednesday, the 5-year-old can be seen busting a move. Related: OMG Justin Trudeau Looks Smitten At Katy Perry's Concert! In the clip, JT performs on the main stage to an adoring crowd. Little does he know there was a performance of its own happening side-stage! Rocking out to the music, Phineas leaps off a speaker.