Sexy, politically incorrect and not at all affected by osteoporosis, Brianna Williams is Mummy Num Nums, faded star and arch nemesis of Bette Midler, desperate to hold on to her youth. She’s definitely not old, not even remotely; in fact, she’s practically a “sexy baby.”

Part sketch and part improvisation, Mummy Num Nums: A Sexy Party is an interactive cabaret introducing its eponymous star to Melbourne Fringe 2017 audiences. Williams is joined by Sophie Kneebone as her ex-lover Dimelza, Isabella Valette as her personal trainer Pam Speedie, and Lee Naimo as Hollywood producer Lee Naimo.

Williams encourages her audience to interact and guide the storyline, contributing to the soundscape and requesting prompts. She demonstrates her confidence and adeptness with corralling the audience, although the preview night audience is admittedly already eager and receptive.

Shoving grapes into Kneebone’s mouth, Williams is at her peak physical comedy. It’s moments like these that showcase Williams’ improvisational talent when bouncing off her co-stars. Unfortunately William’s pre-planned moments and solo improvisation fall flat more often than these shared spontaneous moments.

Conversely, Valette’s consistent improvisational talent and deadpan delivery are unexpected highlights. Valette is delightfully uncomfortable as twitchy personal trainer and sex offender Pam Speedie, maintaining her character even when Naimo and Williams break theirs.

Naimo awkwardly blocks Williams at various stages, and Williams’ solution – after faltering instead of taking charge – seems to be to push the same jokes repeatedly. It’s a little tiresome, as is her oblivious politically incorrect shtick, wherein she attempts to provoke discomfort by making controversial jokes about paedophilia and sexual harassment, but instead falls somewhat flat.

As a whole, the performance feels like a few friends grabbed some props and improvised an entire on the spot. It’s lazy at times and uncomfortable at others, and I hope it’s just preview jitters caused by a few technical errors.