Accidentally on purpose
Con premeditación, alevosía y ventaja

Pictures taken from Google Images, «Accidentally on purpose»
Click on the image to watch some scenes of The Show «Accidentally on purpose»
If you do something on purpose, but you pretend that it was an accident, we say that you do it accidentally on purpose.

Pictures taken from Google Images, «Accidentally on purpose»
Click on the image to know what the show «Accidentally in purpose» is all about.
Origin:
There is a special manner of speech in which we use to contradictory terms together, but the last one is the one that weighs more. This manner of speech is called oxymoron. Some examples are: original copy, a fine mess, a little big, agree to disagree, awfully pretty, intelligently stupid, etc. Accidentally on purpose is one of these expressions.

Pictures taken from Google Images «Accidentally on purpose»
Click on the image to watch the preview of the series «Accidentally on purpose»
Example: