“guess what”
Guess what usually introduces news, rather than seriously asking the listener to guess. It often precedes something exciting or surprising: “Listen to this!”
A2-15 / CEFR A2 / EPISODE 15
Inviting a friend to a concert
SceneTina tells Frank she managed to get tickets.

WORDS & CONTEXT
Guess what usually introduces news, rather than seriously asking the listener to guess. It often precedes something exciting or surprising: “Listen to this!”
Sell out means to be completely sold. It describes popular concert tickets disappearing within minutes of going on sale. Tina was waiting on the website an hour before the sale began and bought the tickets as soon as she could. It does not mean she kept refreshing for an hour after they sold out.
As soon as ... means immediately when something happens, and as soon as I could means the moment it became possible. Here it means she clicked "Buy" right after the sale began and buying became possible.
I'm in. informally accepts a plan or invitation. The opposite, I'm out., declines participation.
Of course you have. responds to Tina's I've already planned everything, with a mixture of recognition and mild exasperation: that is exactly what Frank would expect of her. Of course you do. in A2-38 and Of course you made a list. in A2-60 have the same effect.
Sing along means to sing together with music or a performer. Earplugs are small plugs that block sound. Since Tina announces she will sing every song, Frank says he will bring earplugs for himself. The punchline is that Frank, who "never complains" when she sings, prepares earplugs instead of complaining.