Thomas "Tommy" Jonathan Murphy was an orphan boy to whom Eric acted as a big brother. They spent some time together, and got along excellently. Eric made Tommy laugh all the time, and Tommy seemed to be a bit more intelligent than Eric from time to time (he corrects Eric when Eric mixes up right and left).
Tommy helped Eric pack his stuff and move out from his apartment. He also wanted to visit Eric's baby brother Joshua, who got very sick in the hospital. He urged Eric to adopt him, but when Eric refused after he realized he can't care for Tommy, Tommy became angry. Nonetheless, he gave Eric one last visit before he went to another family who adopted him from California.
He appeared in the Girl Meets World episode, Girl Meets Mr. Squirrels Goes To Washington, where he reunited with Eric after more than 16 years, and in that time understood why Eric gave him up.