Halm has worked primarily in commercials and is also filming the upcoming James Franco-directed biopic on the late German writer Charles Bukowski, in which he plays a young Frank Sullivan.
The series, which picks up with the Matthews now full-grown adults and the parents of two children, follows the couple's young daughter "Riley" and the life lessons that she learns. The titular character of Riley was filled in late January by Spy Kids: All the Time in the World actress Rowan Blanchard.
Fishel, whose most notable acting work was her seven-season stint on Boy Meets World, reacted to the exciting casting news on Twitter.
"If having real life children is as hard as finding these two beauties (@rowblanchard & @teohalm) then I think I'm happy with being a TV mom," she posted. "... We worked so hard to find the perfect kids. We found them. I love them already. Get ready."
Production on Girl Meets World is set to commence later this month. The show is expected to premiere on the Disney Channel in late 2013.