Justin Timberlake and Jimmy Fallon used to debate about who'd cry the most whilst watching kids' movies.

The 40-year-old singer - who has son Silas, two, with wife Jessica Biel - took to Instagram on Tuesday (20.09.17) to pay tribute to his best friend on his 48th birthday and to reveal some of the stuff the ''two bros'' used to get up to, including which of them was a ''nicer'' person and who had better hair.

Alongside a selfie of the pair with Justin cooking on a BBQ in the background while they both sipped beer, the 'Can't Stop The Feeling' singer wrote on Instagram: ''Happy Birthday, @jimmyfallon ‼ Remember that time when we were just two bros hanging out, drinking beer, grilling hamburgers and hot dogs and talking about life and who had the better hairline and who was always the first to crack up in our sketches ... OOOH, and who would probably cry the most at the animated movies our kids watched and who was the nicer one of us two and crazy stuff like why do you park on a driveway and drive on a parkway?! Yeah ... I remember that too! Just two bros. Hanging out. Doing bro stuff. (sic)''

The talk show host's best pal came in useful earlier this year, when the teleprompter failed during his opening monologue - which ended with him joking with the singer-and-actor about his nerves - at the Golden Globe Awards, and though he knew that could happen at any point during the telecast, he didn't expect it at the opening of the show.

Jimmy - who has four-year-old daughter Winnie and Frances, two, with his wife Nancy - joked: ''I was like, it's definitely live! It's definitely real!

''It's like, 'OK ... Justin? Where's Justin Timberlake? Please, Justin, help me out on this one, what do I do?'

''I didn't memorise my monologue but I knew maybe the teleprompter might go out at one point, but I didn't imagine the first opening of the show.

''If I have any problem in life, I'm like, 'Where's Justin Timberlake?' and he usually solves the problem. Which he did tonight as well.''