Yeah, it's from "Hex Factor", the episode when Wanda, Pietro's sister first appeared. The Brotherhood and the X-Men had a huge fight in the mall and Nightcrawler faced off with Pietro/Quicksilver and then Quicky was like measuring Kurt and stuff, putting all the clothes and dresses and hats on him, (basically playing around with Kurt with his super speed of course) and one of those clothes is that bridal costume. But at the end, Kurt won by teleporting behind Pietro and putting a hat on him and kicking him to the shoe stand.
But at the end still, the Brotherhood won over X-Men because of Wanda's massive powers. 😄