James "Jimmy" Widdle probably has a lot of potty emergencies.
If his name is Cockney Rhyming slang for "piddle", it wouldn't be surprising if he's known for wetting himself. It would also make sense because he didn't want to be in the army.
Widdle was a civilian born and raised in India during the Empire before being called up for the army.
Britain ruled India from the 1760s (the movie is set in 1895), so Widdle's probably from a long ancestry of soldiers that conquered and settled there, making him British, so when he was old enough, he was ordered to do National Service with other young men at the time.
- But the film is explicitly set in the Victorian period, and the United Kingdom didn't introduce conscription until 1916, 16 years after Victoria died. Furthermore, India itself has never had military service, either since independence or under British rule. Widdle's remark "I didn't ask to be a Devil in Skirts" can only mean that he didn't want to be a soldier wearing a kilt, since he can only have joined the army voluntarily.
Keene was responsible for Sid and Shorthouse's honours.
Keene does most of the work, but "looks too incompetent" to be as brilliant as Sid and Shorthouse, so he is never promoted and is overshadowed by them. Meanwhile, Sid and Shorthouse are lazy and abusing their powers in order to get with women.
MacNutt is trolling Widdle.
He doesn't like him so he purposely makes him do the horrible tasks. Widdle losing his underwear just played into MacNutt's hands.
Silk underwear is often seen as fanservice for some. God knows what Keene probably had to do in order to get Indian fashion designers to make him some silk underpants.
After returning from Oxbridge, the Khasi of Khalabar ordered his people to learn English.
How else would the people of Khalabar know how to speak English? Remember, they're not the people that have been occupied.