CP3S said:

I wasn't sure how to look it up either, so I did a copy & paste on twooffour's words "creepy kid at locomotive" and put "Back to the Future 3" in front of it on a google search. Turns out he is well known as "creepy kid at the end of Back to the Future III". You can find youtube videos of the scene, but basically while Doc is talking to Jennifer and Marty you can see Doc's son Verne in the background motion with his hand then point to his crotch. 

 

 So in part 3 of the Oliver Twist saga...okay, this is totally off-topic so I won't even pretend.  I just had to say that for a boy getting in trouble, Oliver does something weird with his tonue in literally the last couple seconds of this song.  Noticed it years ago and forgot about it till reading this thread.  Much more visible on the TV, but always made me laugh once I noticed it.  I just had to put that out there.