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5SOS Sing Your Tweets -- Watch!

The guys got goofy on 'The Tonight Show.'

5 Seconds Of Summer popped by "The Tonight Show Starring Jimmy Fallon" on Thursday night (October 2), and I'm happy to report that nobody pooped onstage.

First up, 5SOS sang a bunch of the viewer-submitted #FallSongs tweets, which take the lyrics to well-known songs and alter them to be all autumn-y. (Hmmmmm, why does that sound familiar?) Watch 'em cover everyone from blink-182 ("All the fall things") and Jay Z ("I got Halloween problems, but a witch ain't one") to Nelly ("I am getting so cold, I need a pumpkin latte") and even themselves.

The "Amnesia" singers also performed their latest 5 Seconds Of Summer single, "Good Girls," which, in case you don't know, is all about how "good girls are bad girls who haven't been caught.

There's just one thing that's bothering me about the performance: Why is Michael's hair still red? It's been that color since the iTunes Music Festival, and that was, like, a month ago. I'm worried.