Sneaking someone into my building past the doorman?

I want to sneak my partner into my mom's flat without having the doorman stopping us for questions. My mom will be out of town so I have no worries about her but I'm concerned he'll say something to her.

What plausible excuse can he use if he is questioned?

So far I've thought of us both entering at different timings, and giving another flat number, but aside from that what else can I do? I'm desperate for help!
Updates
+1 y
Added: we may have to get in really late a few days because of this wedding we have to attend so that will draw a lot of attention.
Sneaking someone into my building past the doorman?
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