dragon in (someone's) garage

Translations
воображаемая вещь
He keeps talking about his plans, but they're like a dragon in his garage – not real at all.
Он всё говорит о своих планах, но это как дракон в его гараже – абсолютно нереально.
Definitions
A 'dragon in (someone's) garage' refers to an unfalsifiable claim—something that cannot be proven or disproven because it is defined in such a way that evidence is impossible to obtain. The phrase originates from Carl Sagan's analogy in his book 'The Demon-Haunted World,' where he describes someone claiming to have a dragon in their garage, but every test to detect the dragon is met with an excuse for why it can't be detected. It is often used to illustrate the problem of claims that are immune to scrutiny or scientific testing.