Learn German: Du wirst verrückt! - You are going crazy!

The verb werden means "to become" or "to get." In English, we often say someone is "going crazy" to describe a change of state, but in German, you use werden for this. You cannot use gehen (to go) in this context.

Is wirst an irregular verb form? I expected "werdest".

Yes, werden is a stem-changing irregular verb in the present tense. For the du (you) form, the vowel changes from "e" to "i", and it drops the "d" entirely. This makes it du wirst instead of following the regular pattern.

Why is there no adjective ending on verrückt?

Adjectives don't take any endings when they follow a linking verb like werden (to become) or sein (to be). You only add endings when the adjective is placed directly in front of a noun.

What is the literal meaning of verrückt?

It literally means "shifted" or "moved out of place." It comes from the verb verrücken. So if you are verrückt, your mind is thought of as being shifted out of its normal position!