What do the two Pokemon above have in common?

[MegaPod]

Both have teeth on their tail, one way or another.

Rotom-Heat

 

[Vulpix037]

Both resist Steel type moves.

Magneton

 

[MegaPod]

Both are super duper cool artificial-looking Electric types.

Spheal

 

[Lightning Flame Blast]

Both come from odd numbered generations.

Duskoir

 

[MegaPod]

Both have a spherical body shape.

Porygon-Z

 

[Acrobatic Crobat]

Both are artifical-looking (and, in Porygon's case, actually artifical).

Feebas?

 

[Jyo]

couldn't find much other than both able to learn TM 44 Rest

Pyroar (female)

 

[Rainami]

both have abilities relating to gender -- rivalry affecting pyroar's power based on it, and oblivious making feebas immune to attract

ledian

 

[Lightning Flame Blast]

Both have red body parts (Ledian’s is kind of a pink but hey)

Mamoswine

 

[MegaPod]

Both have a type immunity.

Ditto

 

[Jyo]

tough that time, can't find much
(I'm sure both looking super ugly to me doesn't count)
both seem to be weak to fighting type

Mew

 

[Acrobatic Crobat]

Both same shade of pink (or blue when shiny), can use Transform, have the same weight, seem to be connected. Everyone knows that Mew evolves into Ditto when exposed to steamroller.

Espurr.

 

[MegaPod]

Both are Psycats. Yes, I just made that up.

Pupitar

 

[Vulpix037]

Both have names ending with R.

Steelix

 

[TheGoldenToon]

Both are ground types.

Milotic

 

[Isaac the Investigator]

Both are serpentine.

Cresselia.

 

[Lightning Flame Blast]

Both are majestic.

Quagsire

 

[Jyo]

Both seem to not be liked by me

Luxray

 

[Isaac the Investigator]

Both are PU

Trumbeak

 

[Arylett Charnoa]

Both have small amounts of red in their color scheme.

Ninetales.