In passing, hijacking is where one passer decides to change what pattern they are passing and their actions transitions their partner into a compatible pattern. Collectively these are also known as "programming" because you are programming your partner. Most people use programming and hijacking interchangeably.
Brook Roberts´ article on passing 4-handed siteswaps with 5 clubs in the IJA ezine eJuggle. Contains descriptions of patterns like Parsnip, 5 club WhyNot and NotWhy as well as short videos and advice for learning/teaching.
If you stay inside the vanilla restriction, you´ll get 4 handed siteswaps with hands throwing alternately. This means, a 4 handed ‘global’ siteswap sequence gives you the throws for right hand juggler 1, right hand juggler 2, left hand juggler 1, left hand juggler 2 and again. So, juggler 2 starts half a beat after juggler 1 and they never throw at the same time.
Let´s start easy, funny and entertaining with vanilla siteswap, explained at the 'Nerd Nite' in Magdeburg, November 2014 by Alexander Leymann (in German, but the slides are very useful!). If you prefer further reading, here is the link to Allen Knutsons Siteswap FAQ