The actress was on set at the long-running drama this week to play a prospective girlfriend for show favourite Karl Kennedy (Alan Fletcher).
Platt previously starred on Neighbours for a year from 1995, portraying medical student Jen Handley.
Speaking of her brief return, Platt commented: "It was definitely deja vu sitting in the make-up room - and to be playing opposite Fletch, who I worked with all those years ago, is hilarious."
She added: "[It's a] different character and very different time - the internet was a complete unknown when I was first on Neighbours."
Platt's storyline will see her character arrange a date with Karl after they meet online.
The episodes in question will air in Australia in October, before being screened on Channel 5 in the UK the following month.