All of the other reindeer used to laugh and call him names. They never let poor Rudolph join in any reindeer games.
15 seconds sound clip from the Rudolph and Frosty: Christmas in July movie soundboard.
You can hear this line at 00:14:32 in the Blu-ray version of the movie.
Quote context
[...]
- Can't you make up your mind, my little one?
- Flew 300 miles in only 15 leaps when I heard the news and...
- Oh! Will you just look at him? My little buck. We'll name him Rudolph!
- O eye of snow, what's this you show?
- A red-nosed reindeer? So that's how Santa defeated my snow dragons.
- It will be a different story next Christmas Eve.
[...]