5 Seconds of Summer made their 'Tonight Show' debut last night (Oct. 2) -- and they certainly made the most of it.

The Aussie band was the musical guest on the show and delivered an energetic and fun version of their song 'Good Girls,' which you can see in the video above. But Luke, Calum, Michael and Ashton ended up doing so much more, including taking part in a hilarious bit with host Jimmy Fallon that had them singing about pumpkin lattes and flu shots.

As part of a #FallSongs segment, 5SOS performed musical renditions of tweets that fans had posted earlier in the day. The whole bit was hilarious and the guys adorably played along, goofing around with Fallon and even teasing a possible name change. Plus: a backstage clip featuring them sharing "My First Album" was a web exclusive. Watch videos of both segments below!

5 Seconds of Summer Perform #FallSongs

5SOS Share Their First Albums

Bonus: See Michael, Ashton + More Celebs' Yearbook Photos!

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