Warning: There are some spoilers ahead.

A lot of people were pretty upset with the “How I Met Your Mother” finale.

One reason that may explain fans' frustrations is because the finale has been set in stone since the story began.

The final scene with Ted’s teenage kids was filmed eight years ago around the start of season 2. This was primarily done because the creators knew the two actors playing Ted’s kids would age as the show moved forward. (How else did you think Ted’s two teens look ageless throughout the nine-season series?)

After the finale aired, “How I Met Your Mother” actress Cobie Smulders appeared on the “Late Show with David Letterman” to discuss the series’ sendoff and admitted creators Craig Thomas and Carter Bays knew the end since the first episode.

“Carter and Craig are so smart they actually had planned the ending during our pilot,” said Smulders. “They shot some scenes with the two children.”

Of course, this may not be news to die-hard fans of the series. Thomas elaborated more on the pre-recorded ending back in 2008 to Zap2It.

“We've had a plan since the pilot and we actually shot a little piece of it at the beginning of season two, using the kids, because we knew if we waited until the finale of the series, the kids would have aged like six years. So yeah, part of our plan for how we want to end it all has already been done.”

He later told The Chicago Tribune the two actors who play the kids, Lyndsy Fonseca and David Henrie (who's now a cameraman), and executive producer and director Pamela Fryman were among the few who knew the ending to “HIMYM” and kept that secret for nearly a decade.

That’s pretty impressive.

However, the significance of the ending being taped years ago is that no matter what twists and turns the show would take, no matter what character growth and development we would see (especially with Barney), there was always the idea that Ted would somehow end up with Robin.

Thinking it over, that's fine because the show focused more on Robin than the mother (the series probably would have been more aptly called “How I Met Your Stepmother”), and in the end, it all came full circle.

If you’ve been watching since the beginning, we see Robin with her five dogs approached by Ted who comes to her apartment with a stolen blue French horn.

At the series' end, in a nearly identical scene, Ted once again heads to Robin’s apartment with the horn (that he kept for all those years) and offers it to Robin as she hangs her head familiarly out her window.

Despite that, knowing the above final scene was filmed years earlier made Monday's sendoff feel a bit contrived.

If the show was ever in danger of getting canceled, the writers would have little problem tying up the current storyline and reworking it so that it fit with the ending they already had in place.

Yes, it was nice to see the series come full circle, but after spending an entire season focused on a wedding between Barney (Neil Patrick Harris) and Robin (Cobie Smulders), it felt a bit cheap to see the two get a quickie divorce to clear the road for an eventual Robin and Ted pairing.

What did you think of the finale? Do you feel differently knowing a segment of the finale was filmed years ago?