In episodes Come On, Twin Beds, Ted has been seen with a blue French horn.
What does it signify?
In episodes Come On, Twin Beds, Ted has been seen with a blue French horn.
What does it signify?
Excerpt from Wikia, you can check this link for more details
The Blue French Horn first appeared in the Pilot episode, in which Ted steals it for Robin after she saw it in a restaurant called "Carmichaels" and he said it reminded him of a 'Smurf penis' and she said she'd like one for her apartment. From this point onwards, Robin kept in on the mantle in her apartment.
In the final episode, the last shot of the series is Ted holding it for Robin once again outside her door.
Basically, it's a crazy thing that Ted did for Robin on their first date and proposed at the same time. That's why when he starts to feel the same rush for her, he tried to get out of his way to get the blue French horn.
It symbolizes that crazy stupid love from their first date.
The blue French horn represents Ted actively pursuing and doing anything for love. He seeks out Robin throughout the entire series, just as he repeatedly goes out of his way to get the blue French horn. He didn't stumble upon the blue French horn; he went after it. The horn also represents permanence—Ted ultimately gets it back at the end of the series despite having lost it earlier. He can always go back to the horn, as he can always go back to Robin.