Wubba Lubba Dub-Dub is Rick's catchphrase, which he recurrently uses in the show, mostly in season one. He uses this phrase every time he's happy or makes a joke.
Near the end of the episode Meeseeks and Destroy, Rick first invented his catchphrase, using it when he made a joke about the Meeseeks Box. Rick said that his catchphrase was based on Arsenio's catchphrase, which he used on his show.
In the episode Raising Gazorpazorp, Rick returned that catchphrase and made it a recurring thing.
In the episode Ricksy Business, Rick used the catchphrase multiple times, and Birdperson explains to Morty that it in his language it means "I am in great pain, please help me." At the end of the episode, Rick replaced his catchphrase with "I don't give a FUUUUUCK!!!" Although his catchphrase was replaced in this episode, he has been heard using it a few times in Season 2.