It was a sort of bouncy castle with all the players joined up by sticks to make the teams. The TV people told us which bit to stand in and got us to cheer when the presenter James ran around some cones as part of his exercises.
I've learnt that there's a lot of waiting around when they make TV shows - it's not as amazing as I thought it was, it's more of a normal job really.
I'm not scared
Before Fat Nation, if I'd seen celebrities or people from TV on the street, I would have run up to them and screamed. Now I would just go up to them and say hello.
I'm interested in acting, because I like drama at school. Having Fat Nation on my street has given me more confidence
At school me and a friend are going to start going to the gym - that means my new weekly exercise programme will look like this:
Sarah's weekly exercise plan
2 X gym
1 X kickboxing
1 X netball
1 X trampolining
1 X another PE lesson
We will be busking again next Thursday. I've got a drum kit that I could put out in the front garden and I'll either play the drums or the mandolin - probably I will stick to the mandolin."
Sarah, 14, Birmingham
Sarah bounces into the spotlight as she trampolines on the live show and gets a quick fitness tip from the show's expert.
"At the start of the week I got a call from the TV people saying I was going to be on Thursday's live show. They picked me because they knew I'd done stuff for Short Change.
The bit I was in had about 25 people in it, but I was one of the main three. That meant I was in the front row.
I was jumping on a trampoline while a boy on one side did a hula hoop. On the other side CBBC presenter Ortis held up a punch pad and another boy boxed with it.
Georgie the presenter came over to me and I got a special bit of advice from the F team's fitness person Efua Baker.
She told me that trampolining is good for endurance - and could help me because I had come last on the Short Change assault course.
I reckon I'll need more help with other things as well if I'm going to get really healthy.
On the Fat Nation street everyone's got used to having the TV people around. It's not a big deal for us anymore, but people who don't live on the street have tried to get on the show.
On Thursday one group of kids, who didn't live there, were hanging out on the street in the afternoon. They wanted to stay until the filming started so they could get on TV. Just before the programme started some of the residents pointed them out, and they got chucked out!
Cheeky - cheeky
My mum went along to the rounders game this week. There were people there from Eastenders and the Cheeky Girls were the cheerleaders!
The Cheekies sang and danced, a couple of people asked them for autographs but I don't know if they got them or not. The rounders was won by the greens.
On Thursday we did some more busking
to raise money for Birmingham Children's hospital. My Dad played guitar outside the bit where the TV people are based. I came out and played the mandolin with him and we made £50 in half an hour!"
Sarah, 14, Birmingham
Sarah's busking to raise money for the hospital which saved her brother's life.
"Tomorrow (Wednesday) my dad and I are going to busk on the street to raise money for Birmingham Children's hospital.
My younger brother Danny, who's now 10, had a life-threatening problem with his intestines last year and had to have an operation.
He was so ill that the doctors kept him on a feeding tube for 84 days which cost thousands and thousands of pounds.
We just want to say thank you by raising as much money as we can for the hospital and for people with conditions like Danny had.
He is doing much better now although he has a massive scar and isn't fully recovered.
In our band, I play the drums and the mandolin and my dad plays the guitar and sings. I may sing a few songs as well.
1 choc bar = 2 hours ironing
I watched the programme on Thursday night and saw myself in the crowd for a second.
I was with Jo's dad - Jo is one of the stars of the show - and we were holding up cards which said how much exercise you had to do to burn off calories.
One card said it would take two hours or ironing to burn off the calories in a chocolate bar.
After the filming in the street I went to check out the bull ring, like the ones you get at a funfair, which was on the field.
A man who looked like an Italian model showed the crowd how to ride it and then one of the residents tried to stay on for as long as she could.
Line dancing's not as easy as it looks
I also took part in some line dancing. We all had to wear cowboy hats and follow the professionals at the front of the crowd.
Loads of people were able to do it straight away but when everyone turned, I turned the wrong way and trod on people's feet.
The professionals made it look easy, but I've not done it before and I found it quite hard.
Rounders - I'm for the reds!
On Sunday there's going to be a rounders match between presenter Matt and his team and some of the residents.
I'm going to go down to support the street and paint my face red which is the team colour.
I'm off to kick boxing now, but I'll fill you in on what's happening in the street a bit later."
Sarah, 14, Birmingham
Sarah hopes she'll get the chance to cook with Ainsley Harriet.
"I got a phone call from one of the BBC researchers asking me if I would like to cook with Ainsley Harriet and some other children on the programme.
I'm waiting to hear if I'll take part but if I get the chance I'd love to.
It'd be like Ready, Steady, Cook and I'd buy a bag of food to cook with Ainsley.
I'd buy a bag of fruit and groceries to be healthy and learn how to make it taste nice.
I like cooking but I only really make pancakes so It'd be good to have the skills to cook a variety of food.
Caught on camera
I've been taking pictures of the street with my Newsround camera.
I got someone to take a picture of me standing next to presenter Matt Allwright.
I took one of Jo, one of the main people featured in the programme, listening to my dad playing the guitar.
There was a skipping rehearsal two hours before the live filming on Thursday night.
The three girls from the Great British Skipping team were really good. It was quite impressive to see them all skipping together."
Sarah, 14, Birmingham
Sarah has already appeared on the launch programme and is preparing for the second show which will be live.
"For last Thursday's programme loads of us took part in a street skip.
There were three professional skippers and a boxer at the front of the group and the rest of us were behind them skipping.
I was at the back with two younger kids and they showed me how to skip with three ropes at the same time. It was easier than it sounds.
The difficult part was keeping in time and because I was taller than the other kids, they struggled to get the rope over my head.
The instructor at my kick-boxing class encourages me to skip as a way of improving my heart rate. It's a really good form of exercise.
Two glamorous models from a Sunday newspaper visited the street and were teasing us by handing out sausage rolls to all the residents.
Everyone had to stand on a massive weighing machine to find out how much we weighed as a street.
The scales were the size of an articulated lorry and we were all cramped up standing up on it.
All the residents have been weighed individually as well and told the programme's doctor about any health problems they have such as diabetes.
In the programme last Thursday people were asked about their favourite food. My favourites are crisps, chocolate and mushrooms.
I had potatoes and mushrooms and tomatoes for breakfast the other day. Strangely enough, I'm mad about mushrooms and have been since I was a kid.
I do tend to eat chocolate at school if there are no sandwiches left at lunch time.
It would be nice if they put more out or if the local shops sold packs of sandwiches you could pick up in the morning on your way to school.
I reckon loads of kids would buy them for their lunch.
The show on Thursday is going to be live and we've been told to hang out in the street.
The crew don't want to film an empty road so people will be washing their cars, playing football and acting casual.
The fitness instructor is coming round my house this week so I'm keen to see what she has to say.
Sarah, 14, Birmingham
Sarah will also appear on CBBC's Short Change, showing presenter Ortis round her street.
"During the filming, Ortis was in the street pretending he didn't know where to go and I had to say 'You look a bit lost. Come and look round with me.'
I showed him round the street and the temporary BBC studio which has been built in the middle of our road.