Stanislav Yanevski
Anyone who has seen Harry Potter and the Goblet of Fire likely remembers Viktor Krum or Stanislav Yanevski in real life. The actor has bulked up plenty since his Potter days. Aside from pumping iron at the gym, he continued to act and was in the 2011 British movie Resistance. In addition to acting, Yanevski has also been producing some projects and occasionally post on Instagram about Potter-related things. What a dude.
Christian Coulson
Perhaps this one will surprise you. Do you remember the child actor that played the young Tom Riddle in the second installment of the Harry Potter series? Well, his name is Christian Coulson, and he is, of course, all grown up. After his stint in the film, Coulson landed regular TV work in the U.K. and America. However, you probably recognize him for portraying the music video director Damien George in Nashville.