The Muppets (2011)
The Scene: Gary (Jason Segel) and his bro Walter (Peter Linz) aren't sure what they're doing with themselves, prompting an epiphany-ushering song.
The Song: Oscar-winning number 'Man Or Muppet', which also features a cameo from a certain Big Bang Theory regular.
Join In When: The quartet of men and Muppets sit around a piano tinkling.
Dumb & Dumber (1994)
The Scene: "Radio? Who needs the radio?" asks Lloyd (Jim Carrey), before launching into a song with buddy Harry (Jeff Daniels).
The Song: The guys batter their companion with their very own (and very annoying) rendition of 'Mockingbird'.
Join In When: We beg you not to.
Before Sunset (2004)
The Scene: CÈline (Julie Delpy) and Jesse (Ethan Hawke) arrive at CÈline's place, where Jesse asks her to play a song for him.
The Song: CÈline sings 'A Waltz For A Night', a song about their relationship. All together now: aaaaah.
Join In When: This one's a bit personal to join in with, but the next song (Nina Simone's 'Just In Time') is perfect.
The Scene: Evan (Michael Cera) is mistaken for Jimmy's brother by a load of drunk partygoers and forced to sing.
The Song: Evan picks 'These Eyes', and has the partygoers eating out of the palm of his hand.
Join In When: The other guys start singing along.
The Scene: Aladdin has just discovered a grubby lamp. When he gives it a rub, out pops the genie, who introduces himself with a song and a dance.
The Song: The genie pledges you ain't never had a friend like him in, er, 'Friend Like Me'. By the end of the song, we're pretty much convinced.
Join In When: Whenever you can, really - this one's so fast-paced it'd take a musical mastermind to sing along. Or a very committed five year old.
Lost In Translation (2003)
The Scene: Charlotte (Scarlett Johansson) dons a pink wig and hits a couple of Tokyo karaoke bars with Bob (Bill Murray).
The Song: Charlotte confirms she's one cool chick by opting to sing 'Brass In Pocket' - and does a decent job.
Join In When: The lyric "I'm special" comes along. Everybody loves that bit, right?
Blue Valentine (2010)
The Scene: Dean (Ryan Gosling) woos Cindy (Michelle Williams) outside a shop by singing a cappella.
The Song: Things get sort of prophetic with Dean's song choice as he warbles 'You Always Hurt The One You Love'.
Join In When: Cindy adds a little dance to the mix.
(500) Days Of Summer (2009)
The Scene: Before all the heartbreak, Tom (Joseph Gordon-Levitt) gets drunk and clambers up onto the stage in a bar to sing a little karaoke.
The Song: Rocking a sweater vest and a sweaty 'do, Tom kills The Pixies' 'Here Comes Your Man'.
Join In When: And steal Tom's spotlight?
The Little Mermaid (1989)
The Scene: Ariel has gone to sea witch Ursula for help turning into a human so she can get her guy. And Ursula, naturally, is only happy to help.
The Song: Pat Carroll dials her 'diva-o-meter' to the max in 'Poor Unfortunate Souls', venomously spitting out some of Howard Ashman's finest lyrics.
Join In When: Ariel starts to sing. 'Aaaaahhh ahhhh..." etc
Easy A (2010)
The Scene: Olive Penderghast (Emma Stone) hangs out at home all weekend listening to a card that plays Natasha Bedingfield's 'Pocketful Of Sunshine'.
The Song: At first Olive hates the tune, but she's soon humming it before bursting into full-pelt sing-a-long.
Join In When: Olive hits the shower and does a Bueller with her shampooed hair.