Complex sentence: Billy, Mandy and Grim attacks him for getting back after "previous accidents", but he told them that all he ever wanted is a friend so Billy teachs him "The 5 Cs of Friendship".
Split into simpler sentences: Billy, Mandy and Grim attacks him for getting back after "previous accidents". He told them that all he ever wanted is a friend, so Billy teachs him "The 5 Cs of Friendship".