Both "dream come true" and "dream came true" are grammatically correct, but they are used in different contexts.
Dream Come True: This phrase is used when you want to express that your dream is currently becoming a reality or has recently become a reality. For example, "My dream has come true!" means that something you wished for or desired has been fulfilled, and you are experiencing it at the present moment.
Dream Came True: This phrase is used in the past tense to indicate that your dream became a reality at some point in the past. For example, "Last night, my dream came true," implies that your dream was fulfilled on a specific occasion or in the past, and you are talking about it after the event has already happened.
In summary, "dream come true" is used for present or recent fulfillment of a dream, while "dream came true" is used to refer to past fulfillment of a dream. The choice between the two depends on the timing you want to convey in your sentence.