This adds to the 'transparent' feel of the show's experimental processes and also its 'enthusiastic amateur' appeal, which is helped by the enthusiasm, energy, competence and personality quirks of its hosts.
The two main hosts are Jamie Hyneman and Adam Savage.
He is heavily involved in the American geek community, appearing at many conventions and on the lecture circuit, and with a popular Twitter account.
On the show he appears hyperactive, enthusiastic and excited about everything.
He is obsessively interested in movies, sci-fi and various other aspects of nerd culture, and is a self-confessed 'props geek' and collector.
He is much more comfortable than Jamie on-camera, and in fact was at one point an aspiring actor (he did a semester at theatre school, but has no other post-high-school qualifications); he cheerfully humiliates and endangers himself frequently on the show, from donating various personal bodily fluids, to getting his temperature taken rectally on camera, to drowning himself repeatedly in the 'sinking car' myth. He makes fun of both himself and Jamie, and does a notable Jamie impression that involves him hanging his fingers down over his mouth like a moustache.
He has also worked as a concrete inspector, pet store worker and divemaster in the Caribbean. He was the one first approached to be a host of Mythbusters, but he did not think he would be interesting enough to host it on his own, and brought in Adam Savage, with whom he'd worked before.
Tory Belleci (short for Salvatore) is a special effects designer and maker. On the show he appears, again like Adam, somewhat hyperactive, very physical, ready to humiliate himself on-camera, and prone to hurting himself.
He wears a hearing aid as a result of a congenital inner ear condition, and suffers from severe motion sickness. In fanfiction for the show, he is often paired with Jamie.
Jamie Hyneman is perhaps the most memorable host of Mythbusters; although he is much less effusive than Adam and is obviously less comfortable on camera, his personality is a big part of what makes the show work.
The testing of these myths often involves them building outlandish machines or robots, use of a high-speed camera, or putting materials and objects under strains and stresses for which they were not built. Although many of their results are not scientifically viable because of small sample sizes etc., the Mythbusters do follow something resembling scientific process, and make obvious efforts to keep their experiments scientifically plausible while also entertaining television.
The show's production has a certain DIY feel to it; its five hosts are largely unscripted, although seasons 6 and 7 have involved more set-pieces of talking to camera, and various people involved in its production, such as camera crew, researchers and sound engineers, frequently appear on-camera.
He is relentlessly over-sharing about his personal life.