When it comes to expressing the phrase "enter your mindhead", there are various synonyms that can effectively convey the idea. One alternative could be "invade your thoughts", which suggests a forceful penetration into one's mental realm. Another option could be "intrude upon your consciousness", emphasizing the intrusive aspect of an idea or thought. Additionally, "occupy your cognition" conveys the notion of something taking over and occupying one's mental processes. Lastly, "penetrate your psyche" signifies a deep and profound impact on one's mind and psychological well-being. These synonyms offer diverse ways to articulate the concept of an idea or thought penetrating one's mindhead.