Smile to hide every trace of sadness! Broadway fave and Glee guest star Kristin Chenoweth made an appearance January 16 on The Tonight Show with Jay Leno. "The girl with the cute hair cut" sang the standard “Smile” directly to Leno breaking to say, “Now you know Charlie Chaplin wrote that song but tonight, Jay, I sing it for you, the great comedian of our time. Yes, I can’t imagine leaving this show without leaving you with this song.” Leno, who has hosted the late night talk show for over 20 years, is set to sign off the air for his final episode on February 6. Chenoweth will return to Glee for its special two-part 100th episode on March 18 and 25. Check out the video below to see Leno visibly moved by Chenoweth’s rousing rendition of this great American classic and the Tony winner talking her love life and also that she "cut some of her brains off with her hair!" Smile, what’s the use of crying?!