The cinema is a place to ponder life's big questions: What is love? Is there a higher power? What does it mean to be human? Do Androids Dream of Electric Sheep? But it's also a place full of tantalising ambiguities that leave us scratching our heads weeks, months, years, even decades later.
These are the unanswered movie conundrums that wake us up in the middle of the night in a cold sweat to this very day.
1. Is Deckard a replicant? (Blade Runner)
The release of Blade Runner 2049 has rekindled this 35-year-old debate about whether Harrison Ford's Blade Runner, tasked with 'retiring' rogue replicants, is actually one himself. Director Ridley Scott reckons he IS. Star Harrison Ford says he's not. And now the director of the long-awaited sequel Denis Villeneuve won't answer either way.
We suspect this will always be officially ambiguous but given how much 2049 bends over backwards to make sure it's possible he definitely could be, we reckon he is.
2. Is Leo still dreaming? (Inception)
Christopher Nolan's 2010 film ends with Leonardo DiCaprio's Dom Cobb finally reunited with his kids, just like he wanted. Or is he?
The top that is meant to signify whether he is dreaming or awake spins on, ignored. Did we detect a wobble to indicate this is the real world? We'll never know for sure.
3. What's in the briefcase? (Pulp Fiction)
Much of the action of Quentin Tarantino's cult classic centres around Marsellus Wallace's briefcase, which is filled with a mysterious golden light and can be unlocked with the combination '666' (a popular fan theory says it's Wallace's soul).
Tarantino has said that it is just a MacGuffin – originally it was to contain diamonds before the filmmakers decided that was too obvious, and determined to hide its contents from the audience.
(Tarantino made a guest appearance on his then-girlfriend Margaret Cho's TV show All-American Girl, in which he 'revealed' that the case contained a VHS of the film Dorf Goes Auto Racing and a clip-on reading light. We'll leave it up to you to decide if this is canon.)
4. Who is The Thing? (The Thing)
"Why don't we wait here for a little while, see what happens?" The film closes with MacReady (Kurt Russell) and Childs (Keith David) staring at each other across the camp, not knowing who is human and who is a terrifying alien doppelgänger.
Russell thinks trying to work out the answer (particularly with the use of a possibly fictional bottle of gasoline) is beside the point. And don't expect the later prequel (also The Thing) to offer any answers.
5. How do the Three Seashells work? (Demolition Man)
When Sylvester Stallone's Sergeant John Spartan wakes up in 2032 after being cryogenically frozen for 36 years (remember when that was a popular plot device?), his new police colleagues are highly amused by his confusion about a lack of toilet paper.
You see, in the future, toilets come equipped not with loo roll, but the three seashells. We still don't know how that works, but the coppers of the future find the whole thing hilarious.
6. What did Bill Murray whisper to Scarlett Johansson? (Lost in Translation)
The rather poignant ending to Sofia Coppola's Oscar winning drama sees Bill Murray's fading actor Bob whisper something in the ear of Johansson's lonely young woman Charlotte after a tender embrace. Exactly what he said has been long pondered.
Coppola says the script had no specific line and that Murray improvised. This video reckons it's solved the mystery via digitally enhancing the sound, though we're not entirely convinced.
Nicer perhaps not to know. We'd always assumed it was "No one will ever believe you".
7. What's the punchline to John Bender's joke? (The Breakfast Club)
"A naked blonde walks into a bar with a poodle under one arm and a two-foot salami under the other. She lays the poodle on the table. Bartender says, 'I suppose you won't be needing a drink'. Naked lady says..."
John Bender (Judd Nelson) is the rebellious bad boy of the gang of misfits who call themselves The Breakfast Club during one long weekend detention session. Frustrated teacher Vernon locks Bender in a cupboard but he escapes through the vents while telling himself this smutty gag. But what does the naked lady say?!
Apparently Nelson made the joke up – there never was a punchline, which is probably for the best since we can't imagine a world in which this joke would have been actually funny. If you're desperate for an answer, this Redditor came up with something plausible (but not exactly hilarious).
