On Hardball just now, the Tonight Show host leaped onto the MSNBC set for a surprise, playful chat with host Chris Matthews. Leno quipped that Eric Massa is “tickled to death” about his appearance in Washington. Tomorrow night, the comic will be jokester-in-chief at the White House correspondents’ dinner. John F. Harris has a fun interview with Leno up at Politico, dishing on Fawn Hall, Bush 43 pranks, and more.