Looks like it's narrowly avoided a "gunging" on an infantile novelty quiz show from the 1990s.
This is theoretically not an insect egg, but it was produced because of the laying of an insect egg. This is a Gall. Galls are growths produced on plants, usually because of an insect or mite, though fungus and other causes may produce gall-like structures. This is probably the result of a Gall Wasp in the family Cynipidae. The Gall Wasp lays an egg, and when the egg hatches, the larva releases an enzyme that causes the Gall to grow. The Gall Wasp Larva then feeds on the tissue in the Gall. Galls do not harm the plants. Here is a similar photo on BugGuide, and one on Wikimedia.