Continuity mistake: Mrs. Tweedy stretches her gloves out and releases them. The chickens gulp and Mrs. Tweedy walks away. Between these two shots of Mrs. Tweedy, the clouds behind her obviously change.
Continuity mistake: When Mr. Tweedy is collecting eggs, he represents "no eggs" with a little grey line. But when he gives the checklist to Mrs. Tweedy at the inspection, the "no eggs" symbol is a red 0.
Continuity mistake: When Mr. Tweedy collects the eggs, he adds check marks in Tuesday's column on the list he holds. In Monday's column it reads that chickens 276 and 277 did not lay eggs the day before. However, when the list is submitted at the end of the week, there are check marks in Monday's column for chickens 276 and 277, as if they did lay eggs.
Other mistake: When Ginger finds the bottom of Rocky's poster she takes it out and lines it up with the top half ...and it stays there without any sort of support (we see the back of it as she approaches the poster, and there's nothing there which will stick it).
Chosen answer: Because he wanted them all to have something to look forward to, he didn't want to let them down. Plus Rocky is very bigheaded, it would no doubt be embarrassing for him to admit that he couldn't fly.
THGhost