Jay Leno to appear as guest on Jimmy Fallon’s ‘Tonight Show’

First Joan Rivers, now Jay Leno: Jimmy Fallon is busy wiping all kinds of bad blood from the “Tonight Show” set.

Leno, Fallon’s predecessor on “Tonight,” is returning to the show as a guest on Friday. It will be his first time back on “Tonight” (other than in a brief skit) since leaving earlier this year.

Leno’s on-again, off-again exit from “Tonight,” of course, was a showbiz opera. In 2009, NBC moved to replace him with Conan O’Brien. But the network reversed itself after a prime-time series starring Leno -- the “Tonight” host since 1992 -- bombed. O’Brien left to start a rival show on TBS and Leno was reinstated on “Tonight” in 2010. His retirement earlier this year was less eventful but still clearly not his preference. He prepared for his exit by hurling barbed jokes at NBC executives for weeks.

Fallon, however, appears eager to assume the role of late-night ambassador, opening “Tonight” even to VIPs who have had troubled histories with the show. He said earlier this year that Leno was welcome to appear on the program at any time.

In March, Fallon invited Rivers to be a guest on the show. The brash comic had been banned for years after a falling-out with “Tonight” host Johnny Carson, her former mentor. Leno later said he had declined to have Rivers on the program out of respect for Carson. Rivers died in September.

It remains to be seen what Leno and Fallon will talk about, but one topic could be David Letterman. Leno’s onetime friend and later foil is retiring next year from CBS’ “Late Show.” Leno reportedly has a standing offer to appear on that program as well, but it’s unclear whether he will go.

Also unknown is whether O’Brien will ever break down and join the have-Jay-on bandwagon.

What do you think of Leno going on Fallon’s show?

Twitter: @scottcollinsLAT