Enclosed Trailer - External outlet

You mention that there's a 100 amp service and a refrigerator but not how it's powered when it isn't parked at your home.

Regardless, probably the safest way to do it would be to wire in a shore-power port such as is used on a boat. Basically, it's an inside-out receptacle, it has male pins instead of a socket. Just be sure to protect it with a transfer switch, lock out switch or place it up high if there's a second way (like onboard generator) to power the system.

NO!

And I hope not :B

First off you would have to have/use a double male extension cord.....one male end plugged into a power source and then the other end of cord plugged into the trailer external outlet. These double male cords are NOT available.....you would have to make one yourself. They are called 'window makers' , 'deadman cords' etc. cause as soon as you plug in one end the exposed lugs on other end are energized/hot----source of electrocution !!!!

Would it work........sure. Electricity will flow thru the external outlet then thru the circuit breaker and energize the bus bar and feed all closed circuit breakers energizing all circuits feed by them.
And the circuit breaker on the power source would trip if it's amp rating was exceeded feeding the trailer.
And any of the trailers circuit breakers would also trip if load on them exceeded their amp rating.
Circuit breakers aren't directional.........except for GFCIs.
Electricity will flow either direction.

Issue isn't backfeeding trailer...........
The issue is HOW you backfeed it.
Double male cord.............................NO NO NO

How do you energize your 100A power panel....via an external receptacle?
If so just use an adapter so you can plug your power cord into the 20A outlet

Are you wanting to use a suicide cord?