New Haven is known for several things; Pizza, Yale University, and Louis' Lunch.
Louie's (that's how it's pronounced) is supposidly the originator of the hamburger. They also will not (don't even ask) serve a burger with any ketchup. Bring your own packets if you must have ketchup because you won't see it in the restaurant.
What about ketchip for the fries? They don't sell fries here, only potato chips, so you're out of luck. The burgers come with all the standard toppings except for ketchup -- but you won't need it. The burgers come with spices cooked in, and it's a flavor you'll remember for years to come.
Louie has regular hours, but sometimes will open a little earlier or stay open later depending on the time of year.
If you want something to write home about, stop in here. It's inexpensive, and you'll be dining in some real New Haven history!