Sir Gawain was once a knight under King Gregor's court. However, unlike Duke Igthorn, who was exiled for treason, Sir Gawain remained loyal and simply retired upon growing old. He has since amassed a large fortune and remains a noble within Dunwyn.
Sir Gawain has a tendency to frequently tell stories about his life, of which many people find too annoying or too good to be true and laugh him off. He however insists that his stories are true, no matter how exaggerated they may sound.
According to Cavin, when Sir Gawain was his age, he was climbing the northern mountains near Ursalia where he encountered a Gummi Bear bouncing right by him. Although he did not get a clear view of the Gummi's appearance, he did notice that the bear had dropped a Gummi medallion. From that day forth, he came to believe that Gummi bears did exist, and wore the medallion throughout his service as a knight. When he grew older, he decided to hand down the medallion to Cavin as a gift, making him believe that the Gummi Bears existed as well.
Despite being the source to how Cavin came to believe in the Gummi Bears, Sir Gawain only appeared twice within the series.
Sir Gawain first appeared in "Over the River and through the Trolls", in which he and a wagon full of supplies and gold is traveling towards Dunwyn. Along the way, he and the driver of the wagon are ambushed by a group of trolls who steal his valuables. Sir Gawain, along with the help of Cavin and the Gummi Bears, manage to stop the trolls and deliver the goods to Dunwyn without any further incident. Sir Gawain later asks his grandson if he still has the medallion he gave him, but Cavin sadly replies stating that he lost it. Despite this, Sir Gawain tells his grandson that as long as believes in the Gummi Bears, that is what truly matters.
Sir Gawain later appears again in "He who Laughs Last", where he makes a bet with a skeptical Lord Willoughby, who believes he will not find any evidence of the Gummi Bears' existence and thinks Sir Gawain is crazy and should be detained. After failing to persuade King Gregor to arrest him for obstructing the peace of the citizens, Lord Willoughby dares his rival to accept a risky by proving that Gummi Bears exist by an allowed period of time. Both nobles bet their whole fortunes, causing Cavin to worry that his grandfather will lose the bet and his fortune, as well s becoming an embarrassment by the Dunwynians. This however backfires on Willoughby when the Gummi Bears team up with Sir Gawain, causing him to lose his sanity. Sir Gawain wins the bet and keeps his reputation intact and the Gummi Bears' existence a secret, whilst his rival becomes a laughing stock and is arrested for his insane beliefs. He once again reminds his grandson that the Gummi Bears do in fact exist, to which Cavin subtly agrees.