I've been thinking about the 144,000 and them alone being called to heaven. It does not make logical sense, given the promise given to Abraham, which was still thought to be in effect even in the first century, thus should still be in effect today. The promise was: "I shall surely multiply your seed like the stars of the heavens and like the grains of sand that are on the seashore." (Genesis 22:17).
Now, I don't know about you, but I suspect I can get 144,000 grains of sand to fit in a paper cup. According to multiple sources online, there are actually millions of grains of sand in an 8 ounce cup. So, there is a strange bit of logic to saying that only 144,000 = the grains of sand that are on the seashore.
The Insight book, volume 2, page 889 has this gem:
Consequently, God’s promise, “I shall surely multiply your seed like the stars of the heavens and like the grains of sand that are on the seashore,” has a spiritual fulfillment and means that others, who “belong to Christ,” are added as part of Abraham’s seed. (Ge 22:17; Mr 9:41; 1Co 15:23) God did not disclose the number but left it as indeterminate to man as is the number of the stars and the grains of sand. Not until about 96 C.E., in the Revelation to the apostle John, did He reveal that spiritual Israel, those “sealed” with God’s spirit, which is a token of their heavenly inheritance, numbers 144,000 persons.
WTBTS has never been particularly good at math.