They are in the evil parallel universe. Spock gets facial hair, Janeway gets the cast from Frasier. In the timeline, it's after the episode where Neelix and Tuvok merge into the same terrible person, but before the episode where Janeway and Seven of Nine talk about their feelings.

Also, I'm pretty sure the holographic doctor fired his agent after not getting cast for this skit.

It makes the point that David Hyde Pierce and Hologram Doctor have the same presence and speech mannerisms.

It makes the point that Kelsey Grammar and Captain Janeway have the same presence and speech mannerisms.

I wish I could hate Voyager, but my hatred is reserved for Nemesis. Voyager was bad. Nemesis killed the entire franchise.

Nemesis was only the phenomena that finished off an ailing patient.