It should have been an omen: His Tonight Show felt off-topic before it started.
At times, it seemed Leonard was awaiting a portent or an omen.
Some view is as an omen of dread, of blood, of war, or of victory.
1580s, from Latin omen "foreboding," from Old Latin osmen, of unknown origin; perhaps connected with the root of audire "to hear" [OED] or from PIE *o- "to believe, hold as true" (cf. Greek oiomai "I suppose, think, believe").