There are at two specials of this TV show that are not part of the regular seasons:

1. Höhepunkte aus 20 Jahren „Wetten, dass . . .?“, aired 2001-03-17 on ZDF, approximately 3 hours long
2. Das Beste aus 30 Jahren „Wetten, dass..?“, aired 2011-12-03 on ZDFneo, approximately 5 hours long

These should be added to TMDB. I can't do this myself because there is currently no "Specials" season in this show.

TVDB lists precisely these two special episodes, but with very limited metadata. The German page fernsehserien.de lists a few more, but these are making-offs etc. or duplicates.