Jay Leno is coming back to NBC’s Tonight show this Friday, to promote Sunday’s PBS broadcast of the Kennedy Center’s Mark Twain Prize For American Humor — in which Leno’s Tonight replacement Jimmy Fallon, and NBC’s  Late Night host Seth Meyers play a prominent role.

It’s being billed as the first time Leno’s been back on Tonight since signing off last February.  (Yes, he appeared in Fallon’s TV parody, House Of Cue Cards, but the distinction being made here is that this is Leno’s first return as a guest.) Meanwhile, the annual PBS trophy show is going to get a big fat plug on the most popular late-night show on TV  — Leno got this year’s Mark Twain award in a ceremony last month. TV network cross-backslapping at its finest.

Presumably, there will also be some plugging of Leno’s upcoming CNBC series, Jay Leno’s Garage.

Leno’s next late-night guest gig is expected to be at David Letterman’s CBS show, where he has a standing offer to appear some time before Dave retires in ’15.

Leno  famously got the Tonight gig when Johnny Carson retired, beating out Letterman. Leno hosted from 1992 to 2014, with a brief involuntary respite in ’09-10 when Conan O’Brien took over and Leno was moved to primetime. After Conan resigned, rather than let NBC move the iconic show’s timeslot to push Leno back into late-night, Leno returned and hosted until NBC moved him out again, so as to take advantage of its traditional Olympics ratings boost to launch Fallon in the job. Fallon moved the show from California to New York and settled in as the daypart’s ratings ruler.