Possible Clues:

• Fallon's repertoire
• Stand-up comic's material
• Rita Rudner's repertoire
• Some speeches open with them ... as do this puzzle's four longest entries
• Short gag about fine Christmas cracker contents
• Monologue bits
• "A guy walks into a bar . . ." bits
• Isn't serious
• 'Inside' ones may be hard to get
• Laughing stock?