Soon-to-be host Jimmy Fallon appeared as a guest and had some sentimental moments on 'The Tonight Show' with Jay Leno

Jimmy Fallon had a guest spot Monday on The Tonight Show with Jay Leno, and it was actually quite touching. The mutual respect between the late night hosts was clear, and they shared some laughs looking back at both of their first guest appearance on The Tonight Show.

For the past five years, Fallon has hosted Late Night, airing right after The Tonight Show, and Leno has been the host of the legendary show for the past two decades, with a brief hiccup when Conan O'Brien took a shot at the job in 2009. Fallon's new gig will start Feb. 17.

During the show, the two took a look at Fallon's first appearance on The Tonight Show on Sept. 5, 2002 when he was promoting his comedy album The Bathroom Wall. Fallon wore a three-piece suit and had a quirky haircut. "I look like a banker on 'Little House on the Prairie,'" Fallon said with a laugh.

He wasn't the only one with a three-piece suit for his first appearance. Leno put up a photo of the first time he was on the show on March 2, 1977 as guest with Johnny Carson. He wore a mint green suit and had fluffy '70s hair. "You look like a stylish leprechaun," Fallon joked.

Things then got sentimental, still with the inevitable humor, when Fallon pulled out some of his famous "Thank You Notes" from his Late Night segment. He thanked Leno and promised to make him proud.

Leno's final show is slated for Thursday, with guests Billy Crystal and Garth Brooks.

Watch Fallon's "Thank You Notes" segment on The Tonight Show below.