Exclusive Austin & Ally Sneak Peek: Who Doesn't Have a Prom Date?

It's time for prom on Austin & Ally, but why don't either of them have an official date yet?
On Sunday's episode (8/7c, Disney), Ally (Laura Marano) is still waiting for Gavin (Cameron Jebo) to ask her to prom, as seen in the exclusive sneak peek below. Meanwhile, Austin (Ross Lynch) is procrastinating asking Piper (Hayley Erin), but "came up with a great way to do it."

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So what is it? And why can't Jace (Cameron Deane Stewart) go with Trish (Raini Rodriguez)? Find out below.Austin & Ally airs Sundays at 8/7c on Disney.