I liked the part when.., I liked the part where.., I like the part.., I like when..
All these are variations of "I Like The Part..."
I Like The Part... is a sentence used to state the obvious and that you liked it
It is most commonly used in comments on youtube
Say, on a Call of Duty video, an "I Like The Part..." commnet would read: "I like the part where you played Call of Duty."
Some find I Like The Part... comments to be funny