Dancing and street yoga flash mobs will be in Berkhamsted during the next two weeks.
A dance routine will be taught at the Espinosa Chute Centre in Northbridge Road, Berkhamsted, from 7pm to 9pm on Sunday and from 8pm to 9.30pm next Friday.
Participants will then perform it in the crowd, surprising other festival-goers, as performer JonPaul Palombo sings Jimmy.
Organiser Helen Percy said: “We have sold thousands of tickets to BerkoFest – but the flash mob will be a festival surprise; a bit of fun to be had in the crowd and enjoyed by everybody.”
To sign up to one of the £5 dance lessons, ring 01442 818283.
There will also be a street yoga flash mob in Prince Edward Street, Berkhamsted, from 11am to 11.30am on Saturday.
The event is being held to mark the first anniversary of the opening of Bay-Yoga alternative health studio in Berkhamsted High Street.
The road will be closed, so owner Cathy Haworth can host a free yoga session there.
There will be free taster sessions in yoga, pilates and meditation at the base above Costa Coffee from 9am to 2.45pm that day as well.
Other treatments, including holistic therapy, will be on offer from 3pm to 6pm.