Over the course of time, the transfer window has become an intriguing period for Manchester United Football Club. The Red Devils are one of the biggest football clubs in the world and are therefore thrust into the spotlight during the transfer window periods.Since Sir Alex Ferguson was appointed manager of the club, Manchester United have been known to promote academy products. As they became more successful, they started investing in big money transfers on some of the world's best players as well.Manchester United had the knack of attracting the best players in the world during the Sir Alex Ferguson era such as Eric Cantona, Juan Sebastien Veron, Ruud van Nistelrooy, Rio Ferdinand, and Robin van Persie.Since the Scottish manager's retirement, the Red Devils have made transfer headlines more often than not for all the wrong reasons.Manchester United fans have become accustomed to their club being linked with a number of the world's best players in drawn-out transfer sagas, only for the club to eventually fail in their pursuit.The club has often been forced to make panic buys in the eleventh hour that have shocked fans and pundits alike.On that note, we will take a look at 5 Manchester United transfers that came out of nowhere#5 Anthony Martial still plays for Manchester UnitedManchester City v Manchester United - Premier LeagueManchester United were in need of a striker prior to the 2015-16 season. The club had parted ways with Robin van Persie and Radamel Falcao that summer and were desperately short of attacking options. Manchester United were linked with a move for Thomas Muller and Robert Lewandowski, but failed to land any of their top targets.Manchester United signed 19-year-old Anthony Martial from AS Monaco for a massive £36 million on the final day of the transfer window. Prior to his move to Manchester United, Anthony Martial had played just 70 professional games for the French club.Remembering @AnthonyMartial's Manchester United debut goal against Liverpool on his 24th birthday. 🔥 pic.twitter.com/obV3Wh0I0x— B/R Football (@brfootball) December 5, 2019Martial proved to be a massive hit in his first season for the Red Devils, and received the Golden Boy award that year. The Frenchman is still a key member of Manchester United's squad, but has been inconsistent with the club in recent years.#4 Radamel Falcao was a flop signingTottenham Hotspur v Manchester United - Premier LeagueAfter a poor 2013-14 Premier League season that saw Manchester United finish in seventh place, the club were determined to bounce back the following campaign. The Red Devils hired Louis van Gaal as their new manager and signed the likes of Angel Di Maria, Marcos Rojo and Daley Blind during the summer transfer window.The signing that shocked Manchester United fans was that of Radamel Falcao on the final day of the transfer window. The Columbian signed a one-year loan deal with an option to buy for £43.5 million at the end of the season. Falcao was one of the most lethal strikers in Europe prior to his move to Manchester.One of the deadliest strikers in his prime, Radamel Falcao has played for a variety of European giants in his career, playing for Porto, Atlético Madrid, Manchester United, Chelsea and Monaco, scoring over 170 goals to date. pic.twitter.com/jD2fLOvFio— FOOTBALL TRIVIA 365 (@PlayFT365) March 31, 2019The Columbian was, however, a shadow of himself whilst at Manchester United, as he was never able to fully recover from an ACL injury he suffered during his final season with Atletico Madrid. He scored just four goals in 29 appearances for United before being loaned out to Chelsea the following season.