The most hilarious pranks on BBC Radio 1

Visitors coming to Radio 1 should always be on their guard, because nothing is ever quite as it seems. No one is safe, not even Greg James. A benign chat with a famous actor can end with them quoting your song lyrics back at you with eerie precision, a live interview can suddenly grind to a halt because the presenter has disappeared and the airwaves are suddenly dead, and if your name happens to be the same as a furry predator, that's just asking for trouble.

Scott Mills is probably responsible for more on-air pranks than any other Radio 1 presenter. And so with full-time TV survivalist Bear Grylls in the studio, how could he resist getting Chris Stark to dress up as an actual bear and sneak up for a bear hug? Answer: he couldn't. But keep an eye on Chris at the end, and just how winded he is by Bear's chair. That probably wouldn't work in a forest situation, but it's devastatingly effective here.

It says something fascinating about the relationship between Simon Cowell and Amanda Holden that when Simon is asked to ring Amanda as part of Nick Grimshaw's prank call feature Call or Delete, the very first thing she says on answering the phone is, "What have I done? What are you ringing for?" It's a jocular nervousness that makes the prank itself - Simon ringing to tell Amanda she's being replaced on Britain's Got Talent - feel all the more real. Strong nerves are required for this one.

It's very satisfying to watch the tables being turned on a prankster, and after this deliberately awkward encounter with Chris Stark in 2013, Jennifer Aniston was more than willing to help Scott Mills stitch up his comedy partner. All she had to do is be the most awkward and obstructive interviewee she could possibly be, and watch Chris flap and faff as he tries to rescue a rapidly declining situation, and fails.

It's not always clear just who is being pranked in the game Alphabeticall. The guests - in this case Justin Timberlake and Anna Kendrick - who have to manage a conversation in which every sentence begins with the next letter of the alphabet, or the unwitting business owners who receive their call. Matt Edmondson is the puckish ringmaster for this bewildering confrontation, in which Justin and Anna have to discover if there are Trolls toys in Romford.

The premise of this prank is really simple, that people are always so disarmed by flattery they won't notice they're being tricked. So when Scott Mills had Breaking Bad star Bryan Cranston in a studio with Mollie King, he asked Bryan to pretend to be Mollie's biggest fan, and even arranged for pertinent Mollie facts to be piped into Bryan's headphones during their conversation. Watch out for him finishing her song lyrics - singing, no less! - and naming every member of The Saturdays (well, almost).

Putting the SOS into 5SOS, Scott and Chris set up an interview with 5 Seconds of Summer which the band believed was entirely live. So when the two hosts vanished in the middle of a song and didn't come back, the band did what any hardy showbiz pros would do, they stepped up and took over the show, dealing with fake news broadcasts and 'live' calls from listeners as if this was just another normal day at the office.

You may assume that it would be enough fun to watch Greg James's agonised expression as Keith Lemon conducts an impromptu Through the Keyhole investigation of his flat for the cameras, but there's far more to this clip than even this delightful set-up would suggest. Greg's fridge appears to have been tampered with, and his dartboard, and possibly his bathroom mirror too, and there's at least one surprise guest.

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