Catch up TV
Series 1: 19. You Could Run at the Speed of Sound?
A fun run goes wrong when one ambitious runner tries running at the speed of sound.
Source: CBBC
Most recent episodes of Hey You What If?
Hey You What If?
Series 2: 5. You Could Stop Global Warming
Imagine if we had a thermostat that could turn the world temperature down - could we fix global warming? But be careful, a few degrees too far could cause an ice age.
16-03-2026
CBBC
Hey You What If?
Series 2: 6. You Lived On Venus
Venus has acid rain, crushing pressure, and is hotter than an oven, so it might not sound like the ideal place to live. However, up in the clouds it's almost just like home.
13-03-2026
CBBC
Hey You What If?
Series 2: 4. You Needed Two Of You
From cloning to 3D printing, what if we could actually make copies of ourselves?
13-03-2026
CBBC
Hey You What If?
Series 2: 3. We Got Rid Of Bugs
Bugs might be annoying, but we would soon regret it if we got rid of them - all our favourite foods would disappear, and there would be dung everywhere!
12-03-2026
CBBC
Hey You What If?
Series 1: 23. You Could Teleport?
Is it really possible to teleport? Spoiler alert: it could end in disaster!
11-03-2026
CBBC
Hey You What If?
Series 2: 2. You Walked Through Walls
Wouldn't it be cool to be able to walk through walls? From turning into a gas to quantum trickery, we discover why it wouldn't be quite as useful as you'd like.
11-03-2026
CBBC
Hey You What If?
Series 1: 19. You Could Run At The Speed Of Sound?
A fun run goes wrong when one ambitious runner tries running at the speed of sound.
10-03-2026
CBBC
Hey You What If?
Series 2: 1. You Built A Mega Slide
Could you build a slide to the other side of the world? You would need to start in space, use the slippiest slide ever and make sure you have enough supplies before you go down it!
10-03-2026
CBBC
Hey You What If?
Series 1: 3. You Could Take A Lift To Space?
What would happen if there really was a lift that took you all the way up to space?
09-03-2026
CBBC
Hey You What If?
Series 1: 26. You Could Fly Like A Bird?
Anyone can fly like a bird – you just have to travel across the solar system to do it!
09-03-2026
CBBC
Most popular episodes of Hey You What If?
Hey You What If?
Series 1: 19. You Could Run At The Speed Of Sound?
A fun run goes wrong when one ambitious runner tries running at the speed of sound.
10-03-2026
CBBC
Hey You What If?
Series 1: 20. You Try To Catch A Falling Star?
What happens if you try to catch a falling star? Spoiler alert - probably best not to try!
27-02-2026
CBBC
Hey You What If?
Series 1: 14. You Could Live On The Moon?
Some day people will live on the moon – find out just what they are in for.
12-02-2026
CBBC
Hey You What If?
Series 1: 23. You Could Teleport?
Is it really possible to teleport? Spoiler alert: it could end in disaster!
11-03-2026
CBBC
Hey You What If?
Series 1: 2. You Could Dig Through The Earth?
The deepest hole humankind ever dug only got one thousandth of the way through the earth. But what would happen if you kept digging?
27-01-2026
CBBC
Hey You What If?
Series 1: 25. You Could Switch Off The Sun?
See what would happen if you really could switch off the sun.
06-03-2026
CBBC
Hey You What If?
Series 2: 14. You Built A Giant Sandcastle
Is it possible to build a sand castle the size of a real castle? We imagine how it could be done, using a pneumatic drill and a huge, solid gold steamroller!
27-11-2025
CBBC
Hey You What If?
Series 1: 26. You Could Fly Like A Bird?
Anyone can fly like a bird – you just have to travel across the solar system to do it!
09-03-2026
CBBC
Hey You What If?
Series 2: 1. You Built A Mega Slide
Could you build a slide to the other side of the world? You would need to start in space, use the slippiest slide ever and make sure you have enough supplies before you go down it!
10-03-2026
CBBC
Hey You What If?
Series 2: 2. You Walked Through Walls
Wouldn't it be cool to be able to walk through walls? From turning into a gas to quantum trickery, we discover why it wouldn't be quite as useful as you'd like.
11-03-2026
CBBC