1. Modification of objects usually related to fandoms with no malicious intent e.g. Altering of factual information (Wikipedia pages) or images (posters).
1. "Oh my god, _________'s wiki page was totally fandalised by a bunch of pre-pubescent girls!"
Person 1: I just fandalised a Twilight poster!
Person 2: How?
Person 1: I stuck a photo of my face over Bella Swan's!