Teri was always dressed as a teenage girl, a girly-girl who loved lace and frills and silk and satin and heels and makeup and jewelry, especially earrings (although his earlobes were not pierced then), long hair, painted nails (top and bottom), arched brows, in short, anything and everything girly-girl.
Charles liked Teri in a dress because it made their being together on a date look "normal", important to any boy that age.
Teri, for his part, liked the attention of one of the most popular boys in school even though Charles was a cold fish, rude and uncaring for others' feelings, especially with Teri and he was extremely self-centered and introverted.