Shake Shack shares are up 8% just because

Shake Shack is up another 8% on Thursday.

And why not?

Through Wednesday's close, the stock was already up 20% this week, and since its earnings report last Wednesday the stock was up about 22% through Wednesday.

Currently, the stock is trading at around $89.50 per share, giving it a market cap over $3 billion.

This makes it a larger company than JC Penney, Deckers (which makes Ugg boots), and Sotheby's among others (via CNBC's Carl Quintanilla).

Shake Shack went public in January, more than doubled on its first day of trading, and since its IPO priced shares at $21, the stock has more than quadrupled.

Last week, the stock surged and then sold off after its quarterly earnings report - which one analyst called a "historically great" beat-and-raise quarter - but since that wild intraday move the stock has basically only gone up.

The only real news surrounding the company this week is that its flagship Madison Square Park location in New York City re-opened.

Business Insider's office is right around the corner, and when we walked by around lunch-time yesterday, the line was long. So there's that.

Here's the wild move in Shake Shack over the last few days.