Which version of the sentence is correct?

a). My friend came over for dinner, then we went to the movies.
b). My friend came over for dinner, and then we went to the movies.
c). My friend came over for dinner and then we went to the movies.

I think it's C but I'm super conflicted.

Great! Let's go through each option to determine which version of the sentence is correct.

a) "My friend came over for dinner, then we went to the movies."
This option uses the conjunction "then" to connect the two parts of the sentence. "Then" is often used to indicate a sequence of events. However, in this case, it would be more appropriate to use a coordinating conjunction to show a relationship between the two actions.

b) "My friend came over for dinner, and then we went to the movies."
In this option, the coordinating conjunction "and" is used to connect the two actions. This indicates that both actions happened together or in succession.

c) "My friend came over for dinner and then we went to the movies."
Option C combines the actions by simply placing them next to each other without any coordinating conjunction. This usage is often seen in more informal or conversational writing.

Both options b) and c) are correct, but there is a slight difference in emphasis. Option b) emphasizes the sequence of events by explicitly using the coordinating conjunction "and then." Option c) also indicates the sequence but in a more concise and informal manner.

So, ultimately, your choice between b) and c) depends on the specific context and tone you want to convey.