<p>Wireless millirobots engineered to infiltrate intricate vascular networks within living organisms, particularly within constricted and confined spaces, hold immense promise for the future of medical treatments. However, with their multifaceted and intricate designs, some robots often grapple with motion and functionality issues when confronted with tight spaces characterized by small cross-sectional dimensions. In this study, drawing inspiration from the high aspect ratio and undulating swimming patterns of snakes, a millimeter-scale, snake-like robot was designed and fabricated via a combination of extrusion-based four-dimensional (4D) printing and magnetic-responsive intelligent functional inks. A sophisticated motion control strategy was also developed, which enables the robots to perform various dynamic movements, such as undulating swimming, precise turns, graceful circular motions, and coordinated cluster movements, under diverse magnetic field variations. As a potential application, the snake robot can navigate and release drugs in a model coronary intervention vessel with tortuous channels and fluid filling. The novel design and promising applications of this snake robot are invaluable tools in future medical surgeries and interventions.</p>