Welcome to the 20th century.
3 seconds sound clip from the It's the Great Pumpkin, Charlie Brown (1966) movie soundboard.
You can hear this line at 00:11:00.966 in the Blu-ray version of the movie.
Quote context
[...]
- He'll come here because I have the most sincere pumpkin patch, and he respects sincerity.
- Do you really think he'll come?
- Welcome to the 20th century.
- All right, once and for all, are you coming or are you staying? We can't waste all night.
- If you try to hold my hand, I'll slug you.
- Each year the Great Pumpkin rises out of the pumpkin patch that he thinks is the most sincere.
[...]