Another cel I got (actually, a 3 cel set up).
(the background is a reproduction)
The UPN Dilbert series from 1999-2000 were one of the last cartoons to be painted on cels before all the studios switched to digital ink and paint, so this is pretty cool to have.
The Dilbert cel and the woman cel came with original animation drawings (no scans yet, sorry) and one thing I noticed was that parts of the drawing were xeroxed in from a pre-existing drawing, with only the parts moving drawn in. So I guess a form of "tweening" can happen in a hand-drawn cartoon.