What negative (yet funny) experiences does Holling have with Doug Swieteck's brother?
Doug Swietick's brother is never given a proper name. I believe it is because he is representative of faceless bullies that exist in almost any environment where people interact.
Doug's antagonism starts off believable enough. He invites Holling to play in a pick up soccer game at school one day with the intention of flattening Holling. Doug doesn't end up doing it though, because Holling ends up tripping him. Doug flies through the air and hits his head against the goal. Doug tries to stand up and promptly throws up, which is a typical sign and symptom of a severe concussion.
Another Doug and Holling incident involves snowballs. Doug and a few of his friends try to throw yellow snowballs at Holling. Gross.
The last thing that Doug does to Holling is the most devious and well planned. Doug finds a picture of Holling in his Ariel costume and hangs it up in school. Doug doesn't just hang one picture though, he hangs dozens up for several days in a row.