What happened was a famous World Cup clash, not a long-running feud: in the 1990 match between West Germany and the Netherlands, Frank Rijkaard spat at Rudi Völler, and both players were sent off. Völler later accepted Rijkaard’s apology, and they eventually appeared together in a charity-related ad, which helped put the incident behind them.

What the incident was

The moment people usually mean is the spitting incident at Italia ’90, when tensions boiled over in a heated Germany vs Netherlands match. Rijkaard fouled Völler, the situation escalated, and the referee dismissed both men.

Where Patrick Kluivert fits in

Patrick Kluivert was not part of that on-field incident between Völler and Rijkaard. He only appears in later coverage because he was photographed with Rijkaard years afterward, which sometimes gets mixed into the story online.

Why it still comes up

The scene became one of football’s most replayed bad-temper moments, so it gets resurfaced whenever World Cup controversies are discussed. The reason it is remembered so clearly is that Völler handled the humiliation without retaliating, while Rijkaard later apologized.

TL;DR

Nothing happened directly between Rudi Völler and Patrick Kluivert; the famous incident was between Völler and Frank Rijkaard in 1990, and Kluivert is only loosely connected through later Dutch football context.