The bus from TTC to Sea World is a public Lynx bus that just happens to be a direct connection with few stops in between.
There is a way to take a Lynx bus to Universal, but in involves a transfer at the Downtown main station and MANY stops in between.
Mears offers transfers to Universal directly from your resort for around $17.00 PP roundtrip
The day before you wish to go to Universal dial "0" from your Disney resort room phone. When the operator answers ask to be transferred to Mears.
When Mears comes on the line tell them you want to go to Universal the next day, what resort you are staying at, and approximately what time.
They will give you a pickup time and location.
The next day arrive at the pickup location 10 minutes before they state.
When the bus/van arrives pay the driver in CASH the roundtrip fare.
When you arrive at Universal you can schedule a pickup time then OR call the number on your return voucher 2 hours before you wish to return back to your resort.
Return to where you were dropped off about 10 minutes before the agreed upon pickup time.
This is a shared ride, so you will probably stop at other hotels each direction.
If you know you want to use the Mears service to get to Universal and want to use a credit card, stop at the Mears desk at the airport before going to your towncar or Magical Express and purchase Universal Transfer vouchers. That desk is the only place that can take CCs, the drivers cannot.
Even if you purchase vouchers at the airport, you still have to call the day before to reserve the bus.