Chet Donnelly is the main antagonist of the 1985 sci-fi comedy Weird Science and its TV series. Chet is Wyatt's cruel older brother and a military school cadet. He constantly bullies Wyatt and best friend, Gary Wallace. He is portrayed by late Bill Paxton.
When their parents are out of town for the weekend, Chet is called in to watch Wyatt, his and Gary's dismay. When Wyatt arrives late, after going to a bar with Gary and Lisa, Chet threatens to tell their parents about it. However, Wyatt offers Chet a bride to not tell them, which he accepts. When Chet returns home the morning after the party and sees the house a mess, wakes Wyatt, Gary and their new girlfriends up with gun. He scolds and abuses them in kitchen, until Lisa stops him. When Gary and Wyatt leave to take their girlfriends home, Chet flirts with Lisa. However, Lisa, having had enough of Chet's bullying, turns him into a disgusting talking pile of Feces. When Lisa leaves both the house and Chet are returned to normal, just as his parents come home.
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