Angel is a fictional character created by who, and David Greenwalt for the American television programs "Buffy the Vampire Slayer" and its spin-off series "Angel", the character is portrayed by actor David Boreanaz, an American actor, television producer, and director, known for playing vampire-turned-private investigator Angel on "Buffy the Vampire Slayer" (1997–2003) and its spinoff "Angel" (1999–2004)?