Musicians know all about opening acts.
They think long and hard about just who it is that can set the tone for their own artistry. They don't want an act that will duplicate their own sound or provide too jarring a contrast. They need a fit that will intrigue their listeners, open them up to new possibilities and prime them for the main event. Television show producers face the same issues. Show opens need to snag the viewers' attention, draw them in and keep them there through all the commercial and non-commercial interruptions.