He is a knight who is very brave and has quite some fighting skills but also silent. Nobody has ever heard him talk because he has a high squeaky voice, which makes him feel a little embarrassed. He is also known to be a bit clumsy here and there.
Princess Sofia is his biggest fan and tries to help him be himself. During his visit to Enchancia with the other knight, he shows an attraction toward Sofia's Aunt Tilly. Sofia notices this and tries to help the Silent Knight win. He writes a poem for her but gets used as a tissue for Roland to sneeze on, he tries lip singing to her with Sir Maxwell singing for him behind a bush but it ends in disaster, then he tries dancing with her but ends up slipping and sliding across the Ballroom floor.
At the ceremony where Tilly is rewarded with the Shield of Valor, he finally speaks to her and in front of everyone. He admits to her the reason he didn't speak up was because he was afraid of what she might think of his voice and it turns out she loves it.
Sir Bartleby and Tilly get married in, "A Royal Wedding." He doesn't talk at all through the episode, but is extremely happy to be Tilly's husband, which can be seen through his facial expressions.