illusion muscles can be one of two things. one: illusion muscles are when a weak person looking person who looks like he doesnt have any muscles tenses his muscles and his muscles noticeably buldge from his skin, and this person is also quite strong.

the other form of illusion muscles is when, a strong looking person, with big muscles tenses and there is no visible change to his muscle size, this person is also fairly weak.

A buzz word being used to refer to creators and influencers forming or encouraging unhealthy relationships with their fans. Usually used in the context of young audiences feeling they have a relationship with the influencer due to the huge amount of the influencer’s content they consume. The influencer in question, however, is unaware of the fan’s existence other than the general knowledge of having fans. Common examples include Dream and his stans. These relationships are exacerbated by the influencers confirming they have more than a creator-to-viewer relationship.

The word is circulating due to various YouTube essays about the phenomenon using the word, and therefore people who enjoy complaining about influencers repeating what they heard in the video in any comments section they can find.