Sir Toby Belch is the friend of Sir Andrew Aguecheek, or rather Sir Andrew Aguecheek is his friend. He is one of the secondary characters in the play Twelfth Night by William Shakespeare. He is a portly gentleman, but very clever. It is he who comes up with the plot to fool Malvolio.
Sir Toby is Olivia’s uncle and so is often present in her house. He is a knight, but one suspects that this is not a military title but more likely hereditary. He lives by a philosophy of cakes and ale, which at the time was equivalent to hedonism, in fact, when we first meet him he is drunk. His wit is impressive, often spilling elaborate puns or jokes, he greatly aprichiates Maria's plan to fool Malvolio, even promising to marry her. As was customary at the time he has a good knowledge of French, which he uses to taunt the unfortunate Sir Andrew Aguecheek.
He can, however be quite cruel. Locking Malvolio away, claming he is mad is, even he admits, taking a joke too far. He also leeches off Sir Andrew, viewing him as a meal ticket and stool pigeon. He even gets Sir Andrew into a duel when he knows that he cannot fight. Luckily the enemy was a woman named Viola, who was only pretending to be a man, however, Sir Andrew then attacked her much more competent identical, male, twin, Sebastian, Sir Toby looked on, amused as Sir Andrew was beaten up.
As to romance Sir Toby flirts with the maid of the house, Maria, and at the end of the play marries her. When singing drunkenly Sir Toby hints at an active sex life, it seems that in spite of his unsightly body the fairer sex finds him attractive.