JONATHAN MATTISE and KRISTIN M. HALL.

For a 3 1/2-year-old, Elmo sure has sung a lot on “Sesame Street” with some of the best musicians in the world. But it wasn’t until Thursday that the friendly red monster made his Grand Ole Opry debut, a country music rite of passage. Elmo helped ring in the Grand Ole Opry’s 100th anniversary by co-hosting with his “Sesame Street” pal Abby Cadabby. It was a stop on the “Sesame Street” crew’s Road Trip Across America, with stops at professional baseball games, state fairs and corn mazes. Elmo and his other ‘Sesame’ friends have sung with country’s biggest stars for decades, from Johnny Cash to Chris Stapleton.