Dan Lewis

If an artifact affected by Dan Lewis later becomes a creature, Dan's effect no longer applies to it. That artifact will stop being an Equipment and become unattached from any creature it was attached to; it will remain on the battlefield. The same thing happens if Dan leaves the battlefield.

An Equipment that's also a creature can't be equipped to anything unless it has the reconfigure ability.

Although Doctor's companion is a new variant of the partner ability, the rules for partner have not otherwise changed. Notably, Time Lord Doctors and cards with Doctor's companion do not interact with cards which have another partner ability.

The Doctor's companion ability allows you to have two commanders if one has the ability and the other is a legendary creature that is a Time Lord Doctor and has no other creature types. Creatures with the changeling ability, for example, can't be a second commander this way.

Once the game begins, your two commanders are tracked separately. If you cast one, you won't have to pay an additional {2} the first time you cast the other. A player loses the game after having been dealt 21 combat damage from any one of them, not from both of them combined.

If your Commander deck has two commanders, you can include only cards whose own color identities are also found in your commanders' combined color identities.