The Prophet Salla Allahu alaihi wa sallam ordered us not to sit in a masjid until we pray 2 rak’ah. The most authentic opinion is that these two rak’ah must be prayed anytime of the day or night.
If a person prays any 2 rak’ah such as the Sunnah prayers or if a person joins the congregation directly without praying any prior rak’ah, it isn’t recommended nor mandatory to pray 2 rak’ah afterwards as the mandatory prayer sufficed for it.