How Peloton, Pilates, and HIIT Help Tiffani Thiessen Sleep Soundly The Saved by the Bell actor shares how she unwinds. By Michelle Konstantinovsky Hard-core Tiffani Thiessen fans will be delighted to know the former Saved by the Bell and Beverly Hills 90210 star exudes all the bubbliness of Kelly Kapowski with none of the bite of Valerie Malone. But one trait that distinguishes Thiessen from her…