Set 1967 is an example for a bonus pack that contains sets from different, unrelated themes.
Bonus Packs, also called Value Packs, are product bundles that contain several LEGO sets at once. Usually the contained sets are not available elsewhere, in contrast to Product Collections, which feature sets that can also be bought separately. The main selling points of Bonus Packs is the inclusion of exclusive models and a lower pricing when compared to individual purchases of comparable sets.
Bonus packs may contain sets related to one specific theme as well as sets of completely different themes. Often, the featured models are packaged separately and have separate building instructions as well, but there are cases when all sets share a common instruction sheet. Sometimes, all sets from one bonus pack have identical reference numbers.