Dawson Casting: 27-year-old Andrew Garfield and 23-year-old Emma Stone as the teenaged Peter and Gwen — though, truth be told, Garfield pulled the role off unlike most actors above their teens. Emma Stone was questionable, but still believable.
Averted with Rhys Ifans as Dr. Connors, as the character's thick accent indicates he's really British. (Although this is also a minor example in that he uses a more generic English accent rather than his own Welsh one.)
Subverted with Andrew Garfield as Peter Parker/Spider-Man, given that he is British-American and was born in California but grew up in Surrey, England & subsequently has an English accent.
The script for Spider-Man 4 which caused Raimi to leave the series and Columbia Pictures opt to simply go for a Continuity Reboot rather than find a new director & cast to continue Raimi's story. For more info on the script itself, see here.
A lot of footage that featured Dr Connors wound up cut from the film, including a brief appearance of his son Billy & a sequence that saw Spider-Man encountering Dr Rathra in Connors' lair after the fight at the school and ultimately ended in the Lizard killing Rathra. These scenes were later included on the DVD.