First, the backstory. Captain America became a superhero when he was given a supersoldier serum by the army. He was immediately endowed with superhuman strength and endurance.

Now the definition:

When someone is incredibly muscular that regular steroids could not have acheived such muscle size. Therefore, the person must be on the same pills that Captain America takes.

The phenomenon of having to come out as bisexual to the same person/people repeatedly because they assumed or hoped that your sexuality was a "phase." Refers less to the holiday and more to the 1993 Bill Murray comedy film in which the main character experiences the same day over and over.