invariably complementary.

“Can I ask you a riddle?”
“Go ahead.”
“Do you like riddles?”
“Is that a riddle?”
“No. That’s a question.”
“I like riddles. The good ones. Is yours good?”
“It’s very good. Okay, here’s my riddle: I’m invariably complementary, dog-eared, I sit on a periscope and order vanilla ice-cream with hazelnut topping straight from the bar. What am I?”
“Hazelnut topping?”
“No, I’m not hazelnut topping.”
“You’re a stuffed animal? Piglet?”
“No, I’m not Piglet.”
“You’re a rocket out of the sky?”
“Naaa, I’m no rocket out of the sky.”
“You’re the dog. Dog-eared? Dog?”
“No, I’m not the dog.”
“Okay, I give up. What are you?”
“I don’t know.”
“Well, you should. Otherwise it’s not a riddle. A riddle must have an answer.”
“Alright, let’s do it again. I’m invariably complementary, dog-eared, I sit on a periscope and order vanilla ice-cream with hazelnut topping straight from the bar. What am I?”
“You’re yourself.”
“No, I’m not myself. I mean, of course, I am myself, but not in the riddle.”
“You are your best friend, Ben.”
“No, I’m not Ben. And Ben’s not me.”
“You’re two diamonds and a nickel.”
“I’m no diamond or nickel.”
“Okay, I give up. What are you?”
“The dog. I’m the dog. Dog-eared. Get it?”
“But that was my guess before.”
“That was the first riddle. This is the new one.”
“Ah. Okay.”
“So was it a good one? My riddle?”
“Dog-eared, huh? That’s a good one.”