With very few exceptions, the mechanisms used to request/introduce blue traps (and blue sparks) in DK Jr. are identical to those used in the original DK. In fact, nearly all of the machinery used to decide on forward “throws” or “skull” barrels (the unusually marked blue flammable barrels) have been retained but are, in effect, rendered inoperative. Even sections of code specifically written to update DK or erase barrels from a nearly depleted stack are still present. Presumably, they update sprites which have been moved offscreen (they still update registers in the OAM).
While there are still checks for special handling with the first three “barrels” (meant to be thrown, rolled, and rolled, respectfully), and there is still a 1 and 16 chance of “throwing” subsequent “barrels”, none of this has nearly any effect on the object introduced. In fact, the only thing that moves is Mario (and the lever he pushes and pulls on the “electricity” level). There is also some feeble (abnormally slow) animation when the blue spark is being readied to make its circuit.
One possible unusual consequence of being marked as a “skull” barrel is that the object’s pointage is probably randomly determined when squashed by a fruit. This remains to be tested, though.