In one overstuffed stretch, our TVs will be full of endings and beginnings. On Sunday through May 27, that brings:

• The final episodes of two shows that changed television — "Lost" and "24."

• The season finales of the two top-rated series, "Dancing With the Stars" and "American Idol."

• The season openers of two key summer shows, "Bachelorette" and "So You Think You Can Dance."

Those should bring an emotional punch. "There is a final moment that is very, very specific to the series finale," said "24" producer Howard Gordon. "It (provides) a punctuation mark."

And it wraps up an era when producers tried some new things.

First was Fox's "24" in 2001, spreading each story over a full season. Then ABC's "Lost," filmed entirely on O'ahu, showed up in 2004, daring to leap between time frames, continents, even realities.

"It proved that you could do serialized shows that were going to be challenging to the audience, that people could invest in," said Stephen McPherson, the ABC programming chief.

That worked partly because both shows had rich production values. "Lost" became "a gigantic movie," McPherson said; so did "24" ... which is, in fact, planning a movie version next.

And it worked because of scheduling decisions: "Lost" and "24" skip reruns; they cram all the episodes together into the second half of the season. And they promised viewers an ending.

"Lost" was allowed to wrap up with three seasons, totaling 48 hours. That provided time to plan and alter. The only thing the producers promise is that it won't be a safe or simple ending.

"I don't think it would be 'Lost' if there weren't sort of an ongoing and active debate ... as to whether or not it was a good ending," said producer Damon Lindelof. "(Some will) say it's the worst ending in the history of television. And, hopefully to balance them out, my mom will ... "

Meanwhile, "24" has managed to deliver a big ending at the end of each season. "Any number of seasons in years past ... could have been a really, really cool series finale," Gordon said.

Along the way, Jack Bauer (Kiefer Sutherland) has been battered physically and emotionally.

"You feel the accumulated scars of his experience and the weight of his actions for eight years," Gordon said. "Jack has never been able to sort of snap back."

This year, the show dangled a love interest (Renee) in front of him, then killed her. That set him on a rogue path, against the two women who have been his trusted allies, Gordon said. It became "Chloe versus Jack versus President Taylor. We're taking all these characters to places that we've never seen them before. We knew it constituted a risk."

Everything about these shows is risky, of course. There's repetition (Jack dying and being revived, his family being kidnapped and escaping); there are miracles (conquering city traffic).

And there are wild stretches of logic. This year, a felon hid her identity and got a high-security job.

"Even when these moments felt somewhat preposterous or strained," Gordon said, "hopefully, they were always interesting. Even if you wanted to sort of yell at the TV."

Much can seem strained, when heroes become villains on "24" and Locke becomes a smoke monster on "Lost." Still, the shows were big and bold; soon, they'll be gone.