Monday was a big night for Jimmy Fallon , as he took the reins as host of his first Tonight Show. Jimmy had plenty of support for his debut, with Kim Kardashian , Lindsay Lohan , Tina Fey , and Sarah Jessica Parker  all joining in on the fun for his $100 bet skit . The star power kept coming with his first guest, Will Smith , who helped him dance through the "Evolution of Hip-Hop Dancing,"  and U2, who performed at Top of the Rock. Jimmy's still bringing star power; Tuesday night he had Jerry Seinfeld  and Kristen Wiig — who dressed up like Harry Styles  — join him in front of the cameras, and Wednesday was all about Bradley Cooper , Emma Thompson , and Tim McGraw . Thursday brought Will Ferrell  and First Lady Michelle Obama, who were game for an appearance on Jimmy's series "Ew!" . Scroll down to see all the stars so far and get excited for Justin Timberlake 's appearance tonight!