Simplify the following text for a Grade 6 native English-speaking person.
Original: He appeared on Buffy from 1997 to 1999 , at which point he began starring in Angel , which ran until 2004 , with some guest appearances on Buffy after his departure .
Simplified: He appeared on Buffy from 1997 to 1999 , at which point he began starring in Angel , which ran until 2004 .