Continuity mistake: When Josh just becomes big, he hands his baby sister a wallet. She lowers her hands beneath the border of the playpen. The immediate angle, barely a frame later, shows her hands above it. (00:14:45)
Continuity mistake: When Josh and Billy are in the equipment room note the orange and blue pads on the middle shelf. The blue pads change, their white strap goes being tucked up to hanging down then they disappear completely and reappear between shots. (00:16:35)
Continuity mistake: Susan's hands change position on Josh's neck as she says goodbye at the end. (02:04:10)
Continuity mistake: John Heard's racquet jumps from one hand to the other when he and Tom Hanks fight on the tennis court. (01:17:20)
Answer: Paul (John Heard) tells Josh that the serve has to cross the yellow line. When Josh calls the ball short, Paul is basically trying to cheat and claims he never said the ball has to cross the line. Although I'm trying to figure out what racquet sport their playing. It looks like they're playing on a handball court, but the racquet sports I know, the ball has to cross the short line (the yellow line in "Big") on the serve but you also serve from a service area where you have to stand in front of the short line, which they don't do.
Bishop73