How big can oblong balloons be?

There are large, round balloons that are big enough and someone goes up in the balloon.

There are videos on YouTube where someone is stuck in a big balloon.

Is there something like this with long balloons? What is the largest size for long balloons? For example, someone could lie down and place their body, starting from the neck, into an long balloon, which is then inflated.

What would large, oblong balloons be used for? For example, what purpose would it serve if a person were lying down and also inside an inflated, oblong balloon?