Next up for the young actor was "Angels in the Endzone", an ABC "Wonderful World of Disney" TV-movie sequel to the successful 1994 feature "Angels in the Outfield", this time centering around high school football instead of major league baseball. Here Gallagher starred as Kevin, the younger brother of distraught high school football player Jesse (Matthew Lawrence), who blames their father's tragic death on the team's legendary losing streak. The action begins when Kevin asks for divine intervention to get the team, and Jesse, back on the winning track. In 2000, the actor took on the role of Marty in "Hide and Shriek: A New Spin & Marty Adventure", ABC's revisiting of the popular 1950s mystery adventure series.
Gallagher's film debut came in 1993 with a starring role as Mikey Ubriacco in "Look Who's Talking Now", the "now the dogs are talking!" entry into the three part franchise starring John Travolta and Kirstie Alley. He followed up with another role opposite Travolta, this time as the son of the actor's love interest Kyra Sedgwick in 1996's "Phenomenon". The direct-to-video feature "Richie Rich's Christmas Wish" (1998) had Gallagher taking over the title role from Macauley Culkin in this second live-action adaptation of Hanna-Barbera's animated series about a millionaire child.
In addition to his film credits and numerous television appearances, Gallagher appeared onstage in 1994 as the young Scrooge in the seasonal hit "A Christmas Carol", performed at Madison Square Garden's Paramount Theater.