"What was that all about?"

The older guy at the end was mouthing out the lyrics while watching the kids of today singing the Dragon Ball opening.

Basically, he's remembering a song from his youth that kids of today are getting to enjoy.

Pretty much everyone that was a kid back in 1986 and up while the series was on TV in Japan has already grown up, so they're bound to have fond memories of the series if they followed it as kids.

The US definitely doesn't have that nostalgic feeling for two reasons.

1) Dragon Ball aired in its entirety first. Then came Dragon Ball Z. In the US, we had the first 13 episodes and then Z kicked in. We missed a lot during the initial airing. A lot of DB ended up being spoiled and none of the mystery remained when they got around to airing the rest of it due to DBZ having spoiled it.

2) Dragon Ball, as a franchise, never left the US. Even after it finished airing, it stuck around in some manner. Dragon Ball left Japan after GT finished in 1997. It wasn't until the video games (Budokai), the Kanzenban releases and Dragon Box remasters where Japan got to experience Dragon Ball all over again.