*Among the multiple surprises on Thursday’s “American Idol” broadcast – not the least of which was Casey Abrams being voted off, then, saved by the judges – was the unannounced appearance of Stevie Wonder – apropos considering this was Motown week on the show.

During the opening group number, the contestants – all dressed in formal wear – suddenly lined up on either side of the big screen, which opened to reveal the Motown legend. Tyler appeared to be the most pleasantly surprised, collapsing in delight onto fellow judge Jennifer Lopez.

Not only did Stevie perform his hit “Signed, Sealed, Delivered” with the contestants, but he sang his hit version of “Happy Birthday” to Tyler, who turns 63 on Saturday (March 26).

All the contestants lined up to sing along as J.Lo and Randy Jackson brought Steven up on stage for the tribute. Naima held up a painting of the rock star, while Lauren and Pia held a birthday cake  with three candles.

Watch below.