Your dream is rich with symbolism and may reflect various aspects of your life and emotions. Here are some interpretations of different elements in your dream:

1. Kindergarten birthday party: This setting may represent nostalgia and a longing for simpler times. It could also indicate a desire to reconnect with your childhood innocence or joy.
2. Ex-arch nemesis: The presence of someone you have a history with, especially a rivalry, may symbolize unresolved conflicts or feelings from your past. It might suggest that there are lingering emotions or issues from that time that you need to address.
3. Marble and clay busts: Statues can represent fixed ideas or aspects of yourself or others that you may feel are unchanging or lifeless. The fact that they start talking and then grow bodies could indicate that you are becoming more aware of these aspects or feelings, perhaps those that you've suppressed or ignored.
4. Chasing and danger: Being chased in a dream often reflects feelings of anxiety or stress in your waking life. It could suggest that you are trying to escape from something that is troubling you or a fear that you are facing.
5. Clay statue with a knife: This particularly intense imagery may symbolize a fear of betrayal or harm, especially from something that seems harmless or inanimate. It could also represent a part of yourself that you feel is threatening or aggressive.
6. Waking up in your grandparents' house: This transition in your dream might indicate a shift in your emotional state or a return to a place of comfort or safety, yet it is juxtaposed with the fear of the statue, suggesting a struggle between safety and fear.

Overall, this dream seems to reflect a combination of nostalgia, unresolved conflicts, and underlying fears or anxieties. It may be beneficial to explore these feelings further in your waking life, perhaps reflecting on any current situations that resonate with the themes presented in your dream. Journaling or discussing these dreams with someone you trust might help you gain clarity.