You must complete the 3rd level, Zeppelin of consequences.
In this level, you must rescue 5 ambassadors against child labor.
1. The first one is at the beginning of the level. Simply use the special ability of the 2 special children in the jails to distract the bullies, and you'll be able to free him.
2. One ambassador is trapped behind a gas screen. Use the huge opera lady and sing near the gas. She will inhale all the gas and free the ambassador.
3. One ambassador is stuck in a castle, behind a drawbridge. Using an Irish man, punch the bell next to the ring with the big wrestler. He will come down and give you a wedgie. Use him and his wedgie ability to open the gate.
4. One ambassador is in a jail, where you will be sent also. Use the fireman in the cell to extinguish the fire in the fireplace, and get out.
5. The last ambassador is stuck in a race car driven by monkeys... Use a photographer to take a picture of the monkeys and the car will stop.
Once all ambassadors are free, jump in all of them in order, and use the biggest ambassador's ability to unlock the special exit door. Then jump in the biggest chair next to the engine, and unstack so that all dolls are blowing air on the fire. With Charlie, go under them and tap A to light the fire and complete the mission!