The Scene: As things start to look at bit bleak in Paul Thomas Anderson's drama, the entire cast break into (subdued) song.
The Song: Aimee Mann and the film's cast croon 'Wise Up' to heartbreaking effect. "It's not going to stopÖ"
Join In When: Whenever you feel like it, really. That's what the cast do.
O Brother, Where Art Thou? (2000)
The Scene: The Soggy Bottom Boys (George Clooney, John Turturro, Tim Blake Nelson) don fake beards and hop up onto the stage for a damn catchy number.
The Song: The Boys sing 'I'm A Man Of Constant Sorrow' as the crowd claps and cheers.
Join In When: A rude interruption is dealt with the singing starts up again.
Mean Girls (2004)
The Scene: Cady (Lindsay Lohan) and the other mean girls mime along to 'Jingle Bell Rock' during a Christmas show, but then Gretchen (Lacey Chabert) kicks the CD player and leaves them tuneless.
The Song: Cady takes up the tune herself, saving the entire show. Meanwhile, Ms Norbury (Tina Fey) hops onto the piano.
Join In When: Cady starts singing. It's only fair that we help her out.
Breakfast At Tiffany's (1961)
The Scene: Fred (George Peppard) sits typing at his desk when, through the window, he hears an angel's voice come floating down...
The Song: In fact it's Holly (Audrey Hepburn), sitting on her windowsill crooning 'Moon River' in a bewitchingly husky whisper.
Join In When: An orchestra subtly arrives to accompany her.
A Clockwork Orange (1971)
The Scene: Alex (Malcolm McDowell) and his droogs break into the country home of F Alexander to wreak a little havoc.
The Song: While doling out terrible violence, Alex joyfully sings 'Singin' In the Rain'.
Join In When: We wouldn't recommend joining in with this particularly upsetting rendition of the ditty.
The Scene: Mrs. Deagle (Polly Holliday) can't stand Christmas carollers, but she's in for a bit of a shock this year...
The Song: When Mrs Deagle goes outside to throw watcher on the carollers, she discovers a gaggle of Gremlins having a go at Christmas spirit.
Join In When: Mrs Deagle starts screaming. That's if you can decipher the lyrics, which seem to mostly consist of "ya ya yaaa yayaya".
10 Things I Hate About You (1999)
The Scene: Patrick (Heath Ledger) is trying to woo Kat (Julia Stiles), but she's proving really frickin' tricky. Cue an impromptu solo on the football field.
The Song: Patrick sings 'Can't Take My Eyes Off Of You', replete with bleacher-steps dancing.
Join In When: The marching band comes to life on the football field for something truly epic. How can Kat resist?
The Muppet Movie (1979)
The Scene: Kermit plays the banjo while chilling out in a swamp in Florida. It's a special, swampy version of Heaven.
The Song: Kermit croons 'Rainbow Connection' while perched on a log and steals away our little hearts.
Join In When: Our favourite frog starts singing: "Someday we'll find it, the rainbow connection"...
The Scene: Danny (John Travolta) and the guys are fixing up his car when inspiration strikesÖ
The Song: The guys launch into musical number 'Grease Lightning', which turns into a full-blown automobile fantasy, replete with one hell of a pair of wheels.
Join In When: The clapping section starts. Cos it's easy.
Ferris Bueller's Day Off (1986)
The Scene: Bueller (Matthew Broderick) proves he really knows how to enjoy his day off by boarding a parade float.
The Song: Our last miming entry (we promise), in which Bueller sings along to 'Danke Schoen'. So joyful it could lift even the heaviest spirit.
Join In When: The song segues into 'Twist And Shout'.