Do you ever feel like a plastic bag?

It’s hard to imagine Katy Perry ever could. On stage, the Firework singer is the centre of her own universe and nothing like a receptacle for the week’s groceries (for those who shop at Coles, at least).

Perry takes fans on a ‘wild ride’.CREDIT:AAP IMAGE/TONY MCDONOUGH

She dangles her perfect legs off a planet, her diamante Cleopatra wig swinging in the vacuumous breeze.

She reclines on a leaf while her equally lithe dancers douse her in glitter from giant salt and pepper shakers – “bon appetit!”.

She marches out of the giant eye framing the stage, our “dark horse” – a “perfect storm” erupting in a cloud of artificial fog.

On this Witness tour there is ample for the eyes. Each song is expertly choreographed, and her eight-strong cohort of bootylicious back-up dancers doesn’t miss a beat.

The costumes are exquisite. The dancers wear TVs for heads, or giant eyeballs framed with lips, referencing her album cover. There are great big inflatable lions and hands, flying clocks, towering thorny roses and venus fly traps.

Perry’s wardrobe ranges from glittering gowns to a silky lounge suit to an LED crop top that flashes “hot” then “cold” then “TGIF”. Gone are her popsicle-coloured pin-up-girl locks; her bleached crew cut instead echoes the edgier notes of her latest album.

The infamous “left shark” who ad-libbed during Perry’s 2015 Super Bowl performance has transcended his meme status and now has his own bit: playing chopsticks on a giant keyboard with his, uh, feet.

There is a lot of fun to be had, no doubt about that. But it’s all just so much distraction.

Perry has some great pop songs and despite a few flat notes (who can fault her for that with several costume changes, some pole dancing and the odd cartwheel) she can definitely sing. We do hear it – especially in the quieter moments, such as her ballads – but mostly her voice plays second fiddle to the voluminous backing track.

Katy Perry’s concerts are a sensory delight. CREDIT:AAP

Or is that her live band? It’s impossible to tell. The guitars she dons are purely decorative, yet we know she can play – as, evidently, can her backing band.

The between-song banter – especially the pandering to the “best city in Australia” – and the saccharine selfie moments with fans also feel false. Who wants “a chance to be on the cover of Melbourne’s finest newspapers tomorrow?” Our print deadline was hours ago but never mind, it’ll be on Instagram before you blink.

We get fireworks, though – real fireworks – for the perfect encore song, Firework.

“Do you ever feel like a plastic bag?”

Now that you mention it, I guess I do feel kind of used and empty…