Last Minute Halloween Costume Inspo ... Cozy Onesies for the Win!

Even the celebs opt for optimal comfort when it comes to Halloween costumes ... Rockin' a onesie eliminates many reasons for a last-minute panic ...

Kelly Rowland proved the squad costume potential -- seen here sportin' "Bluey" with her kiddo. Taylor Swift remained weather-proof, captioning her onesie 'fit ... "Can’t talk right now, I’m doin hot squirrel sh*t 🐿" ... and Rob Gronkowski's may be tall, handsome and mighty, but there's no wrong age for a cow-onsie!