The mother-of-one, who takes over as president of the Secondary Heads Association Cymru this weekend, was a young teacher at Menzies high school in West Bromwich when scenes from Clockwise, the 1986 comedy classic, were filmed there.
In the film Cleese plays a head obsessed with punctuality who suffers a series of disasters en route to making a speech at a conference. And the irony of his increasingly flustered fate is not lost on Ms Halliwell, now deputy head at Bridgend's Ogmore secondary school.
"I am legendary for my time-keeping, I absolutely hate being late," she said. "I always make sure my watch is five minutes fast.
"In the film there's a scene where John Cleese sits in his study watching the kids in the playground. When he sees them doing something they shouldn't, he shouts at them through a Tannoy.
"I always do lunchtime playground duties at Ogmore and when I started I could see there were things happening around the site that I did not like.
The site was so big my voice didn't carry that far so, like John Cleese's character, I started carrying a megaphone.
"The children are quite amused by it and the rest of the staff think I'm a bit odd. I'm known as the "teacher with the Tannoy" and a black plastic bag, because litter is one of my pet hates."
Ms Halliwell, 43, worked for a brief period in sales for Debenhams before she joined a teacher-training college in the Midlands.
"When they asked me why I wanted to be a teacher I told them I wasn't really sure," she laughed. "The truth was I couldn't think of anything else, but once I started I loved it. I found working with youngsters so rewarding simply because it was fun. I also think teachers are wonderful."
Having worked as a history teacher in the Midlands before returning to her native Wales, Ms Halliwell took up the deputy headship at Ogmore six years ago and says the appointment of a female deputy as SHA Cymru president should not raise eyebrows.
"We have been campaigning to get more deputies and assistants involved," she said. "I do not see myself as a token anything because I have never believed in glass ceilings.
"The most important thing is to ensure we are actively involved in forming education policy and having our say and protecting our members' interests," she said.