Jesse Pinkman was originally slated to be written out by the 9th episode. During the hiatus caused by the writers' strike, creator Vince Gilligan, impressed by Aaron Paul's portrayal of Jesse as well as everybody just liking Paul, decided to reinstate the character and have Jesse's fate be given to another character in the finale of the first season.
After binge-watching the entire show in a span of two weeks, Sir Anthony Hopkins wrote a glowing fan letter to Bryan Cranston, praising him and his fellow actors for their incredible acting, as well as lauding the rest of the crew, comparing the series to a "great Shakespearian or Greek tragedy."
RJ Mitte has cerebral palsy in real life. His case is much milder than Walt Junior's. He had to learn to walk with crutches and slow down his speech to play the part.
It was Vince Gilligan's decision to finish the show in season 5. He didn't want to make the mistake many successful shows make by running too long until the quality decreases.
Many fans were surprised that such a successful show had stars who weren't very famous. Vince Gilligan said that this was by choice, and as the show went on he actually rejected big-name stars in favor of lesser-known actors.