Chelsea FC fans had a unusual tradition of throwing up celery during matches. It was particularly at its height in the 2007 League Cup final against Arsenal. The bizarre tradition was sparked by a song from the 1980s. It was a hit with famous Chelsea supporter Mickey Greenaway, humorously involving celery.
The issue grew more serious when Arsenal players Cesc Fabregas was struck with a piece of celery during a game, that caused him to stop the match. As a result, Chelsea banned the vegetable from Stamford Bridge and even established the hotline that could be used to inform anyone who brought celery inside the stadium. The tradition is now fading but traces of it do are seen, particularly at away matches.
Source: The Plantations International Agroforestry Group of Companies