It’s strange that Jell-o gets top billing, brand-wise.
The original “finger gelatin” recipe was called “Knox Blox,” which called for unflavored gelatin and fruit or other juice, sometimes mixed with cream or other ingredients. There’s a version from another recipe box here. Later, Jell-o introduced their Jell-o Jigglers recipe, which is the same concept, just not quite as firm.
From the box of D.W. from Cedar Falls, Iowa.
1 pkg. Knox gelatin, dissolved in 1/4 cup of water
1 pkg. Jell-o (small) any flavor
1-1/4 cups boiling water
Pour in 8 x 8″ pan. Cut in squares when set.