TAMPA, Fla. — There’s a side to Kenan Thompson that few “Saturday Night Live” viewers get to see, when he takes its stage, shortly before each 11:30 p.m. broadcast, to warm up the studio audience with his exuberant cover of the Spencer Davis Group’s “Gimme Some Lovin’.”

“It’s helped me feel like a pivotal presence there,” said Mr. Thompson, who this May completed his record-breaking 15th season on “S.N.L.” “If the warm-up is off, the first couple minutes of the cold open are going to be off. It’s an important tone-setter.”

The rock ’n’ roll ritual is the rare moment when Mr. Thompson will cut loose and allow himself to be the center of attention. Far more often, he can be seen on the show in key supporting roles. There are the eccentric characters who visit the “Weekend Update” desk (like the self-aggrandizing basketball patriarch LaVar Ball and an eerily upbeat neighbor named Willie) or the characters who hold together ensemble pieces (like the host of the fictional game show “Black Jeopardy!” and Steve Harvey, the M.C. of “Celebrity Family Feud”). This past July, his understated reliability helped earn him an Emmy Award nomination as a supporting actor in a comedy series, his first in that category.

Over a decade and a half on “S.N.L.”, Mr. Thompson, 40, has grown to see himself as an integral part of this long-running entertainment franchise. But he had to get past his deeply ingrained modesty to achieve that recalibration.