Catch up TV
Series 1: 25. You Could Switch Off the Sun?
See what would happen if you really could switch off the sun.
Source: CBBC
Most recent episodes of Hey You What If?
Hey You What If?
Series 1: 1. You Fell Into A Black Hole?
Experience the most extraordinary ride in the universe – falling into a black hole.
21-07-2026
CBBC
Hey You What If?
Series 1: 16. You Could Actually Reach For The Stars?
Want to reach for the stars? It would be the journey of a lifetime - literally.
19-06-2026
CBBC
Hey You What If?
Series 1: 15. Everything You Touched Turned To Gold?
What if you could turn things to gold? This episode shows that it might not work out that well.
18-06-2026
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.
17-06-2026
CBBC
Hey You What If?
Series 1: 13. You Could Shrink Yourself?
If you have always wanted to shrink yourself, this is the episode for you!
16-06-2026
CBBC
Hey You What If?
Series 1: 12. You Can't Wait For Christmas?
It really is possible to time travel into the future, and the team show you how!
15-06-2026
CBBC
Hey You What If?
Series 1: 11. We Could Actually Stop Climate Change?
The planet is being destroyed - but this episode demonstrates the things you can do to help save it.
22-05-2026
CBBC
Hey You What If?
Series 1: 10. The Earth Was Flat?
Find out why a flat earth would feel very unflat indeed!
21-05-2026
CBBC
Hey You What If?
Series 1: 9. The Moon Was Made Of Cheese?
Things don’t quite go to plan when the moon turns into cheese.
20-05-2026
CBBC
Hey You What If?
Series 1: 8. The Earth Stopped Spinning?
Find out why stopping the earth from spinning isn’t such a good idea.
19-05-2026
CBBC
Most popular episodes of Hey You What If?
Hey You What If?
Series 2: 15. You Shrunk The Earth
We find out what would happen if you shrank the earth. You could jump higher and move faster, but you would end up with altitude sickness even at sea level.
20-04-2026
CBBC
Hey You What If?
Series 2: 21. You Built The Tallest Building On Earth
So you want to build the tallest building on Earth? Ambitious but good on yer! This episode will tell you how, starting with how not to. \n\nMost tall buildings are tall and th ...
28-04-2026
CBBC
Hey You What If?
Series 1: 5. You Could Go On Holiday To Mars?
Experience the ultimate in long-distance travel - a holiday on Mars!
14-05-2026
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!
27-03-2026
CBBC
Hey You What If?
Series 1: 16. You Could Actually Reach For The Stars?
Want to reach for the stars? It would be the journey of a lifetime - literally.
19-06-2026
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: 25. Earth Ran Out Of Energy
We try out a crazy idea from science fiction to build a giant sphere around the sun and give us more energy than we'll ever need.
05-05-2026
CBBC
Hey You What If?
Series 2: 20. You Threw A Ball Round The World
To throw a ball around the world, you need to start out in space, throw it ten times the speed of a bullet and make sure your ball does not explode when it hits the atmosphere.
27-04-2026
CBBC
Hey You What If?
Series 2: 18. There Were No Colours
Imagine removing all the colours one by one? It would change more than just how things look, and after taking out just three colours, we would not be able to see anything at all!
23-04-2026
CBBC
Hey You What If?
Series 1: 9. The Moon Was Made Of Cheese?
Things don’t quite go to plan when the moon turns into cheese.
20-05-2026
CBBC