A: 周末愉快！ B: 你呢！ What does 你呢！mean? What does "你呢！" mean? Can it be used as "You too", for example:

Person A: 周末愉快！

Person B: 你呢！

Google translate says that "你呢！" means You too, but this dictionary doesn't. My current guess is that it probably is appropriate, but is relatively informal.
你呢 translates to "how about you" and is usually followed by question mark not exclamation mark. 呢 is used as a way to express question.

Google translate sometimes does funny things. Cross check with other sources before trusting it.

If someone says 周末愉快! to you, reply to them with 周末愉快! is a safe bet. Or you can say Thank You.

Followup:

If the example conversation actually happened, it could be that when A says 周末愉快 and B interprets it as a question for how was/will be for your weekends. So B response with a nod and asking A about his/hers. Though even under this circumstance it still seems pretty strange. We don't usually speak in this manner.