The phrase "was on" can be substituted with various synonyms to enhance the language and avoid repetition. Some of the equivalents for "was on" include "appeared", "was present", "was engaged in", "was involved with", "participated in", "took part in", "joined", "attended", "made an appearance", and "showed up". Using synonyms can improve the flow and impact of the sentence and avoid sounding repetitive. It is always beneficial to have a varied vocabulary to express an idea or a thought properly, and using synonyms can help enhance one's writing and speaking abilities.