stand-in; substitute; double; ringer
Refers to a person or thing used as a replacement, often with a connotation of deception or secrecy, such as a body double, a proxy test-taker, or a decoy.
Using a stand-in for an exam is cheating.
He sent a substitute to attend the meeting in his place.
extra noodles; second serving of noodles
Specifically in ramen shops, a refill of noodles added to the remaining broth. Often ordered as 替え玉ください.
I ordered an extra serving of noodles at the ramen shop.
There's still broth left, so can I get a refill of noodles?
He attended the meeting as a stand-in for the president.
Since there was still broth left, I ordered a refill of noodles.
The culprit used a decoy to escape.
Excuse me, could I get a refill of noodles?