The Krusty Krab is the home of the Krabby Patty and plays a role in It's a SpongeBob Christmas! as the normal eatery for all of the Bikini Bottomites. It still includes the classic Krusty Krab sign along with all of the decor you are familiar with from the series.
The Krusty Krab first appeared during the opening theme during SpongeBob's first selection, Santa Has His Eye on Me. SpongeBob enters the Krusty Krab just after leaving Sandy's house. Mr. Krabs is seen to be hanging lights.
The next appearance of the Krusty Krab after Robot Sponge was released by Plankton. After launching a car into a far-away building, the Robot Sponge burns the Krusty Krab pole down, causing it to fall on Mr. Krabs.
It's third appearance is in "Don't Be A Jerk (It's Christmas). This first occurs when SpongeBob is claiming not to interrupt people when they are conversing, then when he tells not to put people down and not to leave the toilet seat up, etc.
It's fourth, and final appearance, is during the ending when Santa finally comes to Bikini Bottom, claiming he is giving everyone coal. He then is confronted by the Robot Sponge, where Santa is forced to try and hide from Robot Sponge.