The Blackguard Syndrome
He first appears in this episode where he's employed by Alpha and helps him to hijack one of MiB's satellites. However, things don't go as planned and he is forced to ask his brother for help. Finally, the MIB agents J and K went into the satellite and fight Dak and Alpha. They are defeated when they are blasted out into open space where Dak can't regenerate (due to lack of oxygen).
The Cold Sweat Syndrome
In this episode, it has been revealed that Alpha and Dak have merged together and have managed to regenerate after entering into a space station. Later, they go to Arctic to obtain an ancient alien ship with the intention of destroying Earth. Once again, Dak asks his brother for help but the agents J and K come to stop them. Dak fights against Agent J but he is eventually defeated and fuses with his brother.