“Hangover”
A hangover is the headache, nausea, and other unpleasant feelings after drinking too much alcohol, typically the next morning. It is also the episode's title.
A2-38 / CEFR A2 / EPISODE 38
Talking about last night and how you feel
SceneThe next morning in Tina's room. She slumps on the sofa.

WORDS & CONTEXT
A hangover is the headache, nausea, and other unpleasant feelings after drinking too much alcohol, typically the next morning. It is also the episode's title.
In the United States, the legal drinking age is twenty-one. A twenty-first birthday is therefore often celebrated as the milestone of being able to drink openly and legally. This is the cultural background to Tina drinking too many cocktails.
Pound means to beat heavily. With a head, pounding describes a strong throbbing headache, a common expression for a hangover.
A marching band plays while marching. Tina exaggerates her throbbing hangover headache by imagining a loud band performing inside her head.
Maybe means perhaps, and lose count means to stop knowing how many there were; the past tense is lost count. Tina is not giving the number she reached before she stopped counting; she is guessing the total. She is not sure of the exact number of drinks.
Literally originally means "exactly as the words say," but in casual speech it is also used for exaggerated emphasis. Here it strengthens Tina's feeling that she is too miserable to get up: "I seriously can't move from this couch." It does not mean her body has actually stopped working.
Of course you do. acknowledges predictable behavior with mild exasperation; see A2-15. Tina reacts this way when Frank says he always stops after one drink.
Tell someone to ... means to ask or instruct someone to do something. That band refers to the marching band Tina used in line 3 to describe her headache. The punchline treats the headache like guests who are still playing after the party has ended, and asks Frank to tell them to go home. There is no real band.