Unicorns

"Hey, I was told you believe in unicorns. Is that true? Ha ha ha!"

"Of course not! That would be ridiculous! I believe in a particular unicorn!"

"Oh! That's totally different. I'm sorry."

Photographic evidence

"The usual skeptics must know that NASA itself examined this photo and certified that there's no digital manipulation."

Laboratory equipment

"This incubator you designed uses a huge amount of electricity, has parts unrelated to its stated purpose, and most of its inner space does not meet the conditions required to maintain microbe cultures."

"But it's finely tuned!"