Lampshaded: "Let me guess, Bob. I can have hard-boiled eggs, hard-boiled eggs, or... let me see... hard-boiled eggs! I mean, we all know it's the only thing you know how to cook!"
Invoked: Everyone in Bob's life loves his hard-boiled eggs, so he never bothers to learn to cook anything else.
Exploited: When the Big Bad captures and brainwashes Bob, he...
A) ... uses Bob to lull people into a false sense of security ("I heard that Bob's hard-boiled eggs are awesome! I just can't wait to see what else he can cook" from distant acquaintances). B) ... uses Bob's other dishes as a Cool and Unusual Punishment.
Defied: Bob learns to cook something else.
Discussed: "Bob, I think you should learn to cook something else. I'm getting bored of these hard-boiled eggs."
Conversed: "Why doesn't Bob cook anything but hard-boiled eggs? Is he a One-Note Cook or what?"
Implied: Bob always serves hard-boiled eggs, but this is never mentioned by any character.
Played For Laughs:
As a Running Gag, Bob serves hard-boiled eggs at every meal.
Alice asks Bob to cook a meatloaf for a family dinner. Bob has never had to cook anything but hard-boiled eggs before, so despite his attempts to follow the recipe he was given, he sets the kitchen on fire. The fire burns Troperville to the ground, and every main character dies except Miriam, who was conveniently out of town. When she learns that all of her friends are dead, she suffers a severe case of Survivor Guilt.