Justin Timberlake and Jessica Biel put their marriage on the line while competing against Jimmy Fallon in his 'Best Friend's Challenge'.

If JT wasn't married to Biel, he might have ended up marrying Jimmy Fallon, because their relationship is tight. Always goofing off together like two naughty schoolboys, the pair have been best friends since they met at MTV's Video Music Awards in 2002.

Now, in a competition against his best friend's wife, Fallon must take on Biel to see who really knows the singer the best. The game goes that Timberlake is asked a series of random questions, from his favourite cocktail, to his "safeword". Fallon and Biel then try and guess the answers correctly, and of course, hilarity ensues.

It all gets very heated, and Fallon throws a strop about a tequila mule cocktail. Biel takes it to the next level and hands back her wedding ring. Have a watch of the antic below: