I offer several biologically-supported suggestions:

1. Like frogs - Pac-Man mounts Ms. Pac-Man in a pond or stream. Ms. Pac-Man releases her eggs into the water. Pac-Man simultaneously releases sperm which fertilizes the eggs.

2. Like fish (eg. freshwater bass species) - Ms. Pac-Man deposits eggs in a nest dug out of gravel. Pac-Man comes along soon thereafter and releases sperm to fertilize the eggs.

3. Like barnacles - Pac-Man has an extremely long, prehensile penis which he extends over the distance between himself and Ms. Pac-Man.

4. Like parthenogenic haplodiploid lizards - Ms. Pac-Man does not require fertilization at all. Her diploid zygotes develop into females, and her haploid zygotes develop into males. Because of an interesting evolutionary holdover, she does require sterile copulation ("going through the motions") with a male (Pac-Man) to ovulate.

5. They don't - They're just good friends.