When Stevie Wonder flubbed the very first lyric to his very first song Saturday night at the MGM Grand Garden Arena, I got the distinct feeling we were in for an unusual night of music. I was right. Over the next two hours and 40 minutes, the 59-year-old entertainer produced one of the most unpredictable arena shows in recent memory.

• The “set list”: Wonder kept his 14-piece backing group on its toes, deviating wildly from his printed 27-song program. A few changes—scrapping classic opener “Love’s in Need of Love Today” for the lesser-known “Bird of Beauty,” for example—were downright disappointing, but no one seemed to be complaining about the addition of early hit “Uptight (Everything’s Alright).”

• Family ties: After introducing his daughter, Aisha Morris, one of four backing vocalists, Wonder showed off her voice for the next several numbers, even handing over the mic for a lead-vocal turn on Nancy Wilson’s “I’m Gonna Laugh You Right Out of My Life.” Later, Wonder brought up a grandson, who enthusiastically banged away on a kid’s drum kit and a son, who tapped meekly on a tambourine.

• Chatting us up: Further adding to the improvisational feel of the concert, Wonder spoke between numbers with surprising frequency. He encouraged the audience to clap along, played call-and-response (no easy task for us, given his still-golden pipes), sent shout-outs to apparent attendees Mike Tyson and Babyface and joked often (“Blind man carries shotgun,” as a warning to would-be suitors of his daughter). Strange stuff, and a ton of fun.