You must be doing something wrong. Balloons are supposed to be round, not square. You must be blowing air into the wrong places. Here, try it again.
14 seconds sound clip from the Happy New Year, Charlie Brown! movie soundboard.
You can hear this line at 00:09:45.886 in the VHS version of the movie.
Quote context
[...]
- He went up to Anna Pavlovna, kissed her hand, presenting her with a...
- I wonder when my Sweet Baboo is going to ask me to the party.
- I am not your Sweet Baboo! And I wouldn't invite you to a garage sale!
- Isn't he the cutest thing? (2)
- You blow up a balloon this way. OK, now let's see you do it.
- Try blowing slower. Now you're getting it.
- Here, I've got another type of balloon. Watch.
- Well, are you taking me to the party or not?
[...]