Boris Pelkowski is Russian violin virtuoso, and Lilly's boyfriend until book five,when she played Seven Minutes in Heaven at Mia's party and she kisses the attractive busboy,eighteen - year - old Jangbu Panasa,instead of Boris.

His habits include tucking his sweater into his pants, breathing through his mouth, and playing the violin in Gifted and Talented Class/program, when everyone else wants him to be quiet. After Lilly dumps him, he goes for a hot chocolate with Lilly's second-best friend, Tina, and falls in love with her instead. Tina admits to Mia beforehand that she always thought of Boris as cute, and Boris probably liked Tina all along, but it took his and Lilly's break up to make him realise it.

During the summer before their sophomore year, he lifts weights, gets laser eye surgery and becomes (by Mia's standards) a hottie. Boris is a "say it like it is or say nothing at all" sort of guy. In the ninth installment, it appears that Boris is in contact with Michael (they were in a band together and became friends), as Boris implores Mia to respond to Michael's emails so that he won't think she's "forgotten" about him.

After Mia's muscular cousin Hank falls in love with Lilly and kisses her, Boris tries to punch him but ends up cracking his knuckles. Lilly and Boris have some things in common, such as not being considered good-looking except to the people who like them (although Boris becomes handsome in the sixth book),both being geniuses and both bluntly honest people.

Tina asks Mia not to tell Boris that he's hot, because Tina thinks he'll dump her for someone thinner, but Mia says that she can see a "love-light" in Boris's eyes when he looks at Tina.

Mia says in book five that underneath the braces and sweater thing,Boris was passably attractive. His screen name is JoshBell2, after his role model, Joshua Bell.

When he is 26, he ditches the violin, dyes his hair purple and becomes an international pop sensation. However, he doesn’t remain loyal to Tina Hakim Baba and frequently cheats on her.