Mohamed Hossam al-Din, Basma Hegazy and Ahmed Tarek were arrested last month after posting the satirical video to TikTok, depicting a woman visiting her fiance behind bars.
They were accused of "spreading false news, joining and funding a terrorist organization and misusing social media", said human rights lawyer Nabeh Elganadi, who was present on Sunday when Egypt's state security prosecution renewed their 15-day detention period.
Charges of false news and terrorism are regularly levelled against dissidents in Egypt, and less often online content creators in the country where an estimated 60,000 political prisoners are behind bars according to human rights groups.
Cairo is frequently criticized for prolonged pre-trial detentions and what rights groups call a "revolving door" prison system, where people are detained on new charges instead of being released.
Elganadi also said labour activist Mohamed Hashem, who "has no relation to the three accused", was being prosecuted under the same case and charges as them.
Hashem had been "arrested earlier in January and ordered released, before re-appearing in state security prosecution", the lawyer said.
Elganadi said the TikTok trio -- who have over a million followers on the platform between them -- were questioned about their online activity.
But lawyers are not allowed to "examine reports by state security prosecution, so we cannot know for sure that video is why they were arrested", he added.
Human rights lawyers have said arrests over social media content were increasing in the North African country.
Last year, four social media comedians were arrested on charges of terrorism and spreading false news over a song that satirized authorities' failure to rein in rampant inflation.
Egypt has faced frequent criticism of its human rights record. During a visit to Cairo last month, US Secretary of State Antony Blinken called on Egyptian President Abdel Fattah al-Sisi to "free all political prisoners", while hailing the "important strides" the country has made.
Hundreds of political prisoners were released last year, though data compiled by human rights groups showed more have been arrested since.