Strange AOD lock screen (virus?) AND Google Ads activity.

[Grovarn]

Earlier this evening (November 4) I was on the phone with a friend, and upon hanging up I put down my phone and locked it.

After a minute or two a really strange lock screen appeared.
Normally, the phone shows an analog clock with the date underneath (plus any notification icons).
This time, however, it showed a big skull with a crown in place of the clock and displayed the date "12:26 MON FEBRUARY 27" above it (The actual time was around 23:50, Monday, Nov 4). It also showed the battery at 100% (even though it was in fact around 30%) and only a missed call icon.

I tried to get a picture of it but had no other camera and screen shot would not work in the locked mode.

EDIT: I noticed that around the same time this happened I got an activity on my google account labeled "Viewed Gmail ads" with the description: "This activity was saved to your Google Account because you were using Ads.".

I have no recollection of doing that.

 

[Grovarn]

UPDATE: The plot thickens.

I found the AOD that showed up on my phone. Apparantly it's available in the "theme store" and is called "King Skull" (the example image even shows the date and time that showed up on my phone).

But this does not explain why this AOD theme was added to my phone for a short while (with accompanied missed call symbol).