Stevie Wonder Sings 'Happy Birthday' to Steven Tyler on 'American Idol' (VIDEO)

We're not sure what changed behind-the-scenes on 'American Idol' (Thu., 8PM ET on FOX), but they actually managed to make their usually-bloated results show must-see TV this week. From the beginning to the surprise ending, it was compelling edge-of-your-seat stuff.

In the spirit of Motown, the first treat came during the group number. After it wrapped, the contestants lined up on either side of the big screen behind the stage, which opened to reveal Motown legend, Stevie Wonder.

After his performance, he surprised Steven Tyler by calling him out and then breaking out into his version of 'Happy Birthday.' The contestants revealed a cake and a trippy painting of the Aerosmith frontman to honor him. The whole affair left the usually unpredictable judge speechless.

'American Idol' airs Wednesdays and Thursdays at 8PM ET on FOX.