Manuel is a well-meaning but disorganised and constantly confused waiter from Barcelona with a limited grasp of the English language and customs. He is constantly verbally and physically assaulted by his boss. He is afraid of Mr. Fawlty's quick temper and violent assaults, yet often expresses his appreciation for being given the position, despite Basil's abusive treatment toward him. Sybil also appears to hold Manuel in low esteem, dryly remarking, "It'd be quicker to train a monkey." When told by either Basil, Sybil or Polly what to do, he frequently answers "sí" ('yes'), and "¿qué?" ('what?') which once led to a particularly harebrained guest (Mrs Richards) believing Basil's name to be "C. K. Watt". Manuel and Polly are both quite scared of Basil. An oft-quoted catchphrase of the character is "I know nothing", from the episode Communication Problems. Other phrases commonly associated with Manuel are "I can speak English, I learn it from a book", "she go crazy" and "Is hamster". By the time of the second series, his English has improved greatly (though a sequence in The Germans implies that he actually improved his English off-screen during the first series, but chose to hide this fact from Basil to make his life easier), although he still has problems understanding specific orders or people, such as Mrs. Richards, owing to her way of talking (and partially due to her own dottiness). He is also very good friends with Polly, who can communicate best with him (Basil claims to have learnt "classical Spanish", whereas Polly speaks the actual language) and often uses him as a model for her sketches. Basil also suggests she take him to the local ice rink in Basil the Rat.
He is known for his passionate patriotism, amplified in The Anniversary when he tries to make Terry the chef let him cook a seafood paella to his mother's recipe. Manuel has a large family in Spain, mentioning in The Wedding Party that he has five brothers and four sisters.
Basil hired Manuel because he was very cheap labour, but Manuel was variedly able to try to bend the situation around on Basil, and then became the brunt of extreme violence: from being hit on the head with various objects like spoons, saucepans, and a moose's head—to being picked up like a ragdoll and forced to do a chore—Manuel has suffered much violent harassment. Basil's excuse for everything Manuel does is "He's from Barcelona", an excuse that Sybil and even Manuel himself once resorted to.
During the episode Basil the Rat, Manuel acquires a common rat while under the impression that it is a Siberian hamster, and names it Basil (likely out of gratitude to his boss). He becomes very emotionally attached to the rat, and even threatens to leave Fawlty Towers altogether if Basil and Sybil dispose of it, to which Basil immediately responds, "Well, goodbye." The episode also highlights the fact that Manuel is rather dim even without the language barrier, as he lets the rat out of its cage for some exercise.