When Kevin partially closes his vest after exposing his Ed Hardy t-shirt, the words clearly disappear.
When Kevin returns and tells the story of what happened to him back in Iraq, his pants briefly change colors right before the flashback.
Joe has no legal right to arrest his son. Since his son is technically AWOL only the MP can legally arrest him.
When Kevin returns & his story is first told, the "Sargent General Major Captain" in the flashback said Kevin was in a coma but to send his parents a letter saying he was dead since it was already printed out. But at the end, he said he faked his death & threw his dogtags down because he knew they wouldn't be able to tell who was who.