This is probably better titled “danger with chemistry” – but watching the video is harmless. It shows one way to fill a balloon with hydrogen:

The reaction is between aluminum and hydrogen chloride, releasing the hydrogen as a gas. The hydrogen chloride comes from household drain cleaner. You can find more detail on the reaction here:

Hydrogen production

An economic analysis is also needed here: isn’t it cheaper to just buy the tank of party helium at Wal-Mart and fill the balloons that way?

Unless your goal is an explosion – in that case, hydrogen is preferred:

See also: How the hydrogen economy might work

[See previous FWC]