He knows because he once saw a guy stick his tongue to a railroad track on a bet.
7 seconds sound clip from the A Christmas Story (1983) movie soundboard.
You can hear this line at 00:14:08 in the Blu-ray version of the movie.
Quote context
[...]
- What does it look like I'm doing, picking goobers?
- Ah, baloney. What would your old man know about anything?
- He knows because he once saw a guy stick his tongue to a railroad track on a bet.
- Come on, guys, wait up! Come on, guys! Come on, guys, wait up.
- I can't get up. I can't get up!
- Ralph! Hey! I can't get up, Ralphie!
[...]