What actors and actresses appeared in Hi-5 - 1998?

You're likely thinking of the Australian children's television show Hi-5, which premiered in 1999, not 1998. The original cast members for the first season of Hi-5 (1999) were:

* Kellie Crawford

* Tim Harding

* Nathan Foley

* Charli Robinson

* Steven Pace

These five performers remained on the show for a couple of years before being replaced by new cast members.