1. Because of things like this.
2. Because of how this saying came so very true. Twice.
3. Because of how they cover up the “holes” in Ted’s memory.
4. Because of this callback.
5. Because The Mother’s name was revealed way back in Episode 9 in the first season.
6. Because of this cunning use of color theory.
7. Because of how precisely clothes were matched.
8. Because of the symbolism of these clouds turning to blue skies.
9. Because Dr. X’s website exists.
10. Because “before a man meets the woman he’ll marry, he’ll make one horrible mistake.”
11. Because Robin Sparkles’ spaceship was also a curling stone because of Canada.
12. Because even in the first shots of the Hoser Hut, there’s Paul Shaffer.
13. Because of this perfect background joke.
14. Because Marshall’s jacket reappears.
15. Because this Rastafarian is eating a “sandwich.”
16. Whenever Marshall went on a trip, he brought back beer – even in Marvin’s stroller.
17. Because the red carcass that Robin’s locket is in has been there the whole damn time.
18. This motorcycle sign was in an episode way before Barney did something that caused it to exist.
No word on the llamas, though.
19. Because they eventually found all the replicas.
20. Because of how the Van Smoot dynasty was so carefully worked into the show.
21. Because Robin kept her promise.
22. Because Barney does use 83 whenever he’s making up a statistic.
23. Because how Barney’s advice was more accurate than he ever expected.
24. Because of this symmetry between the start and the end of the show.