Maybe? Like, how hard is it to put a Tsar Bomba on the asteroid when it's a light-year away? Or, if it came from the Oort cloud, a thousand years before whatever nudged it in, nudged it in?

I don't know. Putting a bomb on a timer on an asteroid seems pretty simple. If we're time traveling, we're also space traveling, because the solar system was about a third of the way around the galaxy at the K.T. event. In comparison, the shift to the impactor 1ly away would be margin-of-error stuff.

There were no constraints posted; no "you can only take a truckload of stuff", or, "you appear on the Earth where that point was at that point in time". I mean, if all you do is travel back in time 1 year without also traveling in space, you're going to be breathing hard vacuum when you come out.

So: I'm assuming:

• I can choose where I come out
• I can take anything I want with my - I'm not traveling Terminator-style
• I can get my hands on a working Tsar Bomba before I go (that'd probably be the hardest, aside from violating the laws of physics)

However, for the other ideas? What's hard about transporting a murder of crows to the Triassic? I don't even have to go myself.