And Jason Alexander, in his pre- Seinfeld era, once led singing, dancing flash mobs in a commercial advertising McDonald’s bygone McD.L.T. sandwich.

And he has helped gain notice for KFC, Chrysler, and, in an elaborate song-and-dance number, McDonald’s now-scuttled McDLT sandwich. You can still find it on YouTube — the commercial, not the ...

Alexander plays the moderator in the mock face-off, introducing himself as a “star of stage, screen and a McDonald’s commercial from 1986.” ...