Dissolve lemon gelatin in 1 cup of boiling water until completely dissolved.

Add 1/4 cup of cool water and rum extract (optional) to the lemon gelatin mixture.

Measure out 3/4 cup of the lemon gelatin mixture.

Stir in 3/4 cup of canned eggnog into the measured gelatin.

Pour the eggnog gelatin mixture into a 6-cup ring mold.

Refrigerate the mold until the eggnog gelatin is set, but not hard, approximately 30 minutes.

Drain the pear halves and mandarin orange sections, reserving the syrup from the pears.

Add water to the reserved pear syrup to make a total of 3/4 cup of liquid.

Dice the pear halves into smaller pieces.

Dissolve the raspberry gelatin in 1 cup of boiling water.

Add the measured pear syrup liquid and the remaining lemon gelatin mixture to the dissolved raspberry gelatin.

Refrigerate the raspberry gelatin mixture until it begins to thicken.

Once thickened, gently fold in the diced pears.

Spoon the raspberry gelatin mixture with pears into the ring mold over the partially set eggnog gelatin layer.

Arrange the mandarin orange sections in the raspberry gelatin mixture near the edge of the mold, pressing them down lightly to ensure they are submerged.

Refrigerate the entire ring mold until completely set and firm, about 4 hours.

To unmold, dip the bottom of the mold briefly in warm water.

Invert a serving plate over the mold and carefully flip to release the Jello ring.