This isn't a real episode, it's completely fake and made up. The real series 5 only had 42 episodes, ten less episodes than what there was for series 1 to 4. Series 5 was only broadcasted on Nicktoons UK.
I'm surprised that IMBD even allows this in first place and I wonder why those fake episodes aren't taken down yet.
Every Horrid Henry series has a huge gap in between them. Series 1 finished airing in 2007 after starting in 2006. The second series first aired in 2009 and ending in 2010. The third series first aired in 2011 and ended in 2012. The fourth series first aired in 2014 and ended in 2015. The fifth series first aired in 2018 and ended in 2019.