1. In 1996, Ted and Marshall are randomly assigned to the same freshman dorm room.
2. At the first party of the year, Ted hits on Lily.
3. The next morning, Lily is "drawn" to Marshall's room when she goes looking for someone to fix her stereo.
4. During the semester break, Ted and Marshall drive across the country together, bonding over The Proclaimers' "I'm Gonna Be," which was the only song they could listen to since the tape player was broken.
5. In 2001, Ted meets Barney in the bathroom at MacLaren’s.
6. In 2005, Lily and Marshall get engaged in their apartment.
7. That same night, Ted meets Robin.
8. On Dec. 31, 2005, Lily and Marshall have the most magical New Year's Eve midnight kiss ever.
9. In spring 2006, Ted steals a blue French horn — again! — and makes it rain to get Robin to go on a second date with him.
10. But the next morning, Ted gets home to find out Lily has left Marshall and moved to San Francisco.
11. A few months later, Barney goes out to San Francisco to tell Lily she needs to come home.
12. In 2006, Lily and Marshall get back together.
13. In November 2006, the slap bet is orchestrated.
14. And Barney, Ted, Marshall, and Lily find out Robin used to be a Canadian teen pop star in named Robin Sparkles.
15. In winter 2007, slap No. 2 is given.
16. In spring 2007, Lily and Marshall get married.
17. On Slapsgiving 2007, slap No. 3 is given.
18. In fall 2009, Ted teaches his first architecture class — in the wrong room.
And little did he know, his future wife was in the classroom.