I have swapped the tag "mask_challenge_(meme)" for the tag "dildo_behind_mask" which is more descriptive.
I also looked around a bit at the original artist posts and "mask challenge" is not really mentioned.
On google "mask challenge" does bring up some memes but non are really with a dildo or something so the connection is a bit vague.

I think that the usage of a more generic tag "dildo_behind_mask" might also allow for this tag to grow a bit beyond the current surrounding pandemic context, like the similar tags "dildo_under_panties", "dildo_under_clothes" and "dildo_under_swimsuit".