This is a dialogue from the TV series Jessie, episode title is The Fear In Our Stars.
-So, the asteroid's not gonna hit Earth?
-Hardly. Look, if you multiply the trajectory of the asteroid by the angle of Earth's rotation, carry the twosie, The asteroid is actually going to... Crash right into Central Park!
I have no idea what the speaker means here.
"Twosie" is a diminutive of "two"; compare onesie-twosie, an idiom meaning in ones and twos, or "twosie" a type of sleepwear in two pieces. This is by analogy with "onesie" which is a better-known word for a single-piece garment originally for small children (hence the diminutive) and now used as sleep/leisure wear by adults.
"Carry the two" is an example of a procedure in arithmetic where you do multiplication (or addition) digit by digit, carrying the excess over to the next column: see this explanation on WikiHow.
So "carry the twosie" is a childish way of doing multiplication, presumably intended for humorous effect.
