Why does maniac invite mars bars to the birthday party and what happened?

Maniac remembered how clueless Grayson was concerning
blacks and their home.  The McNabs were planning a war against the blacks and had built
a pillbox for protection. A military pillbox is a type of bunker (see link for pictures)
for protection during an attack.  The McNabs thought they were going to be attacked by
the black people on the other side of Hector Street.  Mars Bar had been one of Maniac's
main tormentors because Maniac was white.  He called him Jellyfish.  Whites never go
into the black houses and do not know black people, and blacks did not know about white
people.  So he decided to bring Mars Bar to the white party of the McNabs. The father,
John McNabb, challenged Mars presence and then stormed out the room telling everyone to
let him know when "it" (Mars Bar) left.  Then the kids started playing a game in the
pillbox of blacks vs. whites.  As they were arguing about it, one of the Cobras jumped
down from the hole in the ceiling, barely missing Mars Bar. Maniac had to restrain Mars,
and then escorted him to the other side of Hector Street.  Maniac had to admire Mars Bar
though because he had been very scared, but he didn't show it.