Mollie the Giraffe (a female) was played by "Tweet the Giraffe" (a male) also known as the Toys R Us Giraffe. Tweet died on set at the Franklin Park Zoo. Luckliy, Tweet had completed all his scenes for the movie before his passing.
As Griffin cycles through a park he passes a man in a blue blazer sat on a bench. A little farther on a shot over his back sees him approaching another bench on which a man and woman are sat but a face on shot of him having passed the bench shows it's now occupied by the man in the blue blazer
When Shane is first seen throwing lettuce into Bernie the Gorilla's pen, a leaf lands right next to the bucket. In the shot immediately following from the other side, the lettuce leaf is gone without Shane having picked it up or thrown it in.