Discord has a yard sale. He decides to sell off everything he doesn't want, whether it's his or not. This includes a load of stuff that's been lost through wormholes or whatever, including a few items from other shows.

Maybe it's a crossover (maybe it's Megas XLR, but it's probably more fun to see how long it takes to guess. If you don't know the show, you won't miss that much), maybe it's just an excuse to tie a bunch of stealth puns together. Could you tell the difference?