The reason for Cheeseburger Week (if you really, really need one) is to fete the invention of the cheeseburger by one Lionel Sternberger, in 1924, at a restaurant called the Rite Spot. Dog Haus Biergarten will kick off the week on Jan. 11 with, of course, an eating competition (who can eat the most sliders in six minutes; good luck).
Alternatively, if you want to see how many cheeseburgers you can eat in, say, six hours, you can go on a suggested Cheeseburger Crawl, or organize your own crawl out of any number of the many restaurants participating in the weeklong event. These include Haven Gastropub, Kings Row Gastropub and The Counter, which will have a special bison burger loaded with quite a few toppings (Gruyère, tomatoes, fried fennel rings, marinated artichokes, carrot strings, butter lettuce).
And because eating is no fun without publicly announcing your likes, there will be a Cheeseburger Challenge where you can vote online for your favorite lunch-counter burger, your favorite veggie burger and so on. Which you may as well do, since you're Instagramming and tweeting photos of your burger, anyway.
All participating restaurants, and their Cheeseburger Week offerings, can be found on the Pasadena Restaurant Week's website.