I can only guess, and my guess even depends on what "movies" you saw.
Slackit and I found out that the Region 2 DVDs made for the European and Australian region are a little faster than the one produced for region 1 - north America.
It turns out that Region 2 are about 30 seconds to 1 minute faster, so that calculated down to the rather short intro could be the few seconds you talk about.
Technical reason for that is porbably that Futurama has been made for the NTSC format, using 30 pictures per second. Region 2 however uses the PAL format with only 25 pictures per seconds. In the converting process few pictures have been merged, but I guess that every now and then some pictures were even just taken out.
Welcome to PEEL, OddFlame
In case you should need any help on how to get around here smoothly I recommend you to read our little FAQ, the PEELers' FAQ
Enjoy your stay here.