How are idents like these made?
Yes, they need permission. However, the permission to use the characters in image and other promotional material is likely included in the international distribution or syndication agreement.
It almost definitely was done using a chroma key or other intentional compositing technique, as opposed to trying to mask the movements out of footage from the show. Networks, syndicators, and international distributors usually supply their affiliates with promotional materials. Often, these promotional materials include elements that can be built up into a complete promo that fits the affiliate's branding. The distributor will provide suggestions or instructions on just how a particular element should be used, but it is up to the affiliate to put in their own look.