It’s officially spooky season, and stars are wasting no time dressing up for the holiday. Even though we still have a few more days until Halloween, Robert Downey Jr. got into the holiday spirit early when he let his kids, Exton (10) and Avri (7), shave his head in preparation for his upcoming HBO series “The Sympathizer.” However, the kids wanted a pretty big favor in exchange for their help — they wanted their dad to become a human jack-o’-lantern.
Thankfully, Downey was game, and he…