Sounds like there may have been a traffic incident resulting in the buses being delayed or perhaps they personally don't like you and decided to hang and eat donuts just to annoy you.

I'm guessing you're young? It happens when there's a stall earlier in the route that all 4 of them got stuck in, and then when the stall clears, they show up all at once. Next time you're annoyed, call Translink and ask, "where is my bus?" Each one has a GPS so the operator can tell you exactly where your bus is stuck.

They are pack animals and get lonely and scared quite easily if alone for long - especially if traffic or weather are poor. The #20 is so skittish it can't turn corners without a buddy.