Russell Brand filmed scenes performing as rock star Aldous Snow at his sell-out comedy show "Scandalous", in front of 20,000 people, at the O2 arena in London. Jack Black and Jason Segel joined him on stage.
When Aaron wakes up in a London hotel after a night out with Aldous, a game resembling cricket can be seen on the TV in his room. This is not an actual game, but a parody sketch from the Dutch TV show Jiskefet (1990), aptly titled "English sport".
In Forgetting Sarah Marshall, Jonah Hill plays 'Matthew the Waiter' and gives Aldous Snow (played by Russell Brand) his own music demo CD. Jonah Hill goes on to meet Aldous Snow again in Get Him To The Greek, but as a completely different character (Aaron Green), who works for the music label promoting Aldous Snow.
The trivia items below may give away important plot points.
The flight time from London to New York City is approximately 8 1/2 hours. The time difference between the two cities is five hours with London time being ahead. Therefore, there is no way that Aaron and Aldous could be at the Today Show at 8:47 AM, as depicted on the Today Show clock, when the earliest they could have landed in NYC would be approximately 9:30 AM ET after taking the 7:00 AM LT flight. However, since the Today Show runs to 11:00 AM, Infant Sorrow would have still had enough time to perform on the broadcast.